diff --git a/target/product/mainline_system.mk b/target/product/mainline_system.mk
index d75809c..66207df 100644
--- a/target/product/mainline_system.mk
+++ b/target/product/mainline_system.mk
@@ -18,6 +18,8 @@
 $(call inherit-product, $(SRC_TARGET_DIR)/product/handheld_system.mk)
 $(call inherit-product, $(SRC_TARGET_DIR)/product/telephony_system.mk)
 $(call inherit-product, $(SRC_TARGET_DIR)/product/languages_default.mk)
+# Enable updating of APEXes
+$(call inherit-product, $(SRC_TARGET_DIR)/product/updatable_apex.mk)
 # Add adb keys to debuggable AOSP builds (if they exist)
 $(call inherit-product-if-exists, vendor/google/security/adb/vendor_key.mk)
 
diff --git a/target/product/updatable_apex.mk b/target/product/updatable_apex.mk
new file mode 100644
index 0000000..4b31578
--- /dev/null
+++ b/target/product/updatable_apex.mk
@@ -0,0 +1,20 @@
+#
+# Copyright (C) 2019 The Android Open Source Project
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+# Inherit this when the target needs to support updating APEXes
+
+PRODUCT_PROPERTY_OVERRIDES := ro.apex.updatable=true
+PRODUCT_PACKAGES := com.android.apex.cts.shim.v1_prebuilt
diff --git a/tools/releasetools/merge_target_files.py b/tools/releasetools/merge_target_files.py
index 77c774a..e306807 100755
--- a/tools/releasetools/merge_target_files.py
+++ b/tools/releasetools/merge_target_files.py
@@ -13,11 +13,11 @@
 # WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 # License for the specific language governing permissions and limitations under
 # the License.
+"""This script merges two partial target files packages.
 
-"""
-This script merges two partial target files packages (one of which contains
-system files, and the other contains non-system files) together, producing a
-complete target files package that can be used to generate an OTA package.
+One package contains system files, and the other contains non-system files.
+It produces a complete target files package that can be used to generate an
+OTA package.
 
 Usage: merge_target_files.py [args]
 
@@ -126,8 +126,8 @@
     'META/*',
 ]
 
-# default_system_misc_info_keys is a list of keys to obtain from the system instance of
-# META/misc_info.txt. The remaining keys from the other instance.
+# default_system_misc_info_keys is a list of keys to obtain from the system
+# instance of META/misc_info.txt. The remaining keys from the other instance.
 
 default_system_misc_info_keys = [
     'avb_system_hashtree_enable',
@@ -185,10 +185,8 @@
 
   Args:
     target_files: The target files zip archive from which to extract items.
-
     target_files_temp_dir: The temporary directory where the extracted items
-    will land.
-
+      will land.
     extract_item_list: A list of items to extract.
   """
 
@@ -198,9 +196,7 @@
   # zip file. Otherwise, the extraction step will fail.
 
   with zipfile.ZipFile(
-      target_files,
-      'r',
-      allowZip64=True) as target_files_zipfile:
+      target_files, 'r', allowZip64=True) as target_files_zipfile:
     target_files_namelist = target_files_zipfile.namelist()
 
   filtered_extract_item_list = []
@@ -214,18 +210,17 @@
   # Extract from target_files into target_files_temp_dir the
   # filtered_extract_item_list.
 
-  common.UnzipToDir(
-      target_files,
-      target_files_temp_dir,
-      filtered_extract_item_list)
+  common.UnzipToDir(target_files, target_files_temp_dir,
+                    filtered_extract_item_list)
 
 
 def copy_items(from_dir, to_dir, patterns):
   """Similar to extract_items() except uses an input dir instead of zip."""
   file_paths = []
   for dirpath, _, filenames in os.walk(from_dir):
-    file_paths.extend(os.path.relpath(path=os.path.join(dirpath, filename),
-                                      start=from_dir) for filename in filenames)
+    file_paths.extend(
+        os.path.relpath(path=os.path.join(dirpath, filename), start=from_dir)
+        for filename in filenames)
 
   filtered_file_paths = set()
   for pattern in patterns:
@@ -250,26 +245,25 @@
 
   Args:
     config_file_path: The path to the config file to open and read.
+
+  Returns:
+    The list of strings in the config file.
   """
   with open(config_file_path) as config_file:
     return config_file.read().splitlines()
 
 
-def validate_config_lists(
-    system_item_list,
-    system_misc_info_keys,
-    other_item_list):
+def validate_config_lists(system_item_list, system_misc_info_keys,
+                          other_item_list):
   """Performs validations on the merge config lists.
 
   Args:
-    system_item_list: The list of items to extract from the partial
-    system target files package as is.
-
-    system_misc_info_keys: A list of keys to obtain from the system instance
-    of META/misc_info.txt. The remaining keys from the other instance.
-
-    other_item_list: The list of items to extract from the partial
-    other target files package as is.
+    system_item_list: The list of items to extract from the partial system
+      target files package as is.
+    system_misc_info_keys: A list of keys to obtain from the system instance of
+      META/misc_info.txt. The remaining keys from the other instance.
+    other_item_list: The list of items to extract from the partial other target
+      files package as is.
 
   Returns:
     False if a validation fails, otherwise true.
@@ -284,7 +278,7 @@
   # by the default config lists.
   difference = default_combined_item_set.difference(combined_item_set)
   if difference:
-    logger.error('Missing merge config items: %s' % list(difference))
+    logger.error('Missing merge config items: %s', list(difference))
     logger.error('Please ensure missing items are in either the '
                  'system-item-list or other-item-list files provided to '
                  'this script.')
@@ -299,11 +293,10 @@
   return True
 
 
-def process_ab_partitions_txt(
-    system_target_files_temp_dir,
-    other_target_files_temp_dir,
-    output_target_files_temp_dir):
-  """Perform special processing for META/ab_partitions.txt
+def process_ab_partitions_txt(system_target_files_temp_dir,
+                              other_target_files_temp_dir,
+                              output_target_files_temp_dir):
+  """Perform special processing for META/ab_partitions.txt.
 
   This function merges the contents of the META/ab_partitions.txt files from
   the system directory and the other directory, placing the merged result in
@@ -314,22 +307,20 @@
   names.
 
   Args:
-    system_target_files_temp_dir: The name of a directory containing the
-    special items extracted from the system target files package.
-
-    other_target_files_temp_dir: The name of a directory containing the
-    special items extracted from the other target files package.
-
-    output_target_files_temp_dir: The name of a directory that will be used
-    to create the output target files package after all the special cases
-    are processed.
+    system_target_files_temp_dir: The name of a directory containing the special
+      items extracted from the system target files package.
+    other_target_files_temp_dir: The name of a directory containing the special
+      items extracted from the other target files package.
+    output_target_files_temp_dir: The name of a directory that will be used to
+      create the output target files package after all the special cases are
+      processed.
   """
 
-  system_ab_partitions_txt = os.path.join(
-      system_target_files_temp_dir, 'META', 'ab_partitions.txt')
+  system_ab_partitions_txt = os.path.join(system_target_files_temp_dir, 'META',
+                                          'ab_partitions.txt')
 
-  other_ab_partitions_txt = os.path.join(
-      other_target_files_temp_dir, 'META', 'ab_partitions.txt')
+  other_ab_partitions_txt = os.path.join(other_target_files_temp_dir, 'META',
+                                         'ab_partitions.txt')
 
   with open(system_ab_partitions_txt) as f:
     system_ab_partitions = f.read().splitlines()
@@ -339,8 +330,8 @@
 
   output_ab_partitions = set(system_ab_partitions + other_ab_partitions)
 
-  output_ab_partitions_txt = os.path.join(
-      output_target_files_temp_dir, 'META', 'ab_partitions.txt')
+  output_ab_partitions_txt = os.path.join(output_target_files_temp_dir, 'META',
+                                          'ab_partitions.txt')
 
   with open(output_ab_partitions_txt, 'w') as output:
     for partition in sorted(output_ab_partitions):
@@ -348,42 +339,35 @@
 
 
 def append_recovery_to_filesystem_config(output_target_files_temp_dir):
-  """Perform special processing for META/filesystem_config.txt
+  """Perform special processing for META/filesystem_config.txt.
 
   This function appends recovery information to META/filesystem_config.txt
   so that recovery patch regeneration will succeed.
 
   Args:
-    output_target_files_temp_dir: The name of a directory that will be used
-    to create the output target files package after all the special cases
-    are processed. We find filesystem_config.txt here.
+    output_target_files_temp_dir: The name of a directory that will be used to
+      create the output target files package after all the special cases are
+      processed. We find filesystem_config.txt here.
   """
 
-  filesystem_config_txt = os.path.join(
-      output_target_files_temp_dir,
-      'META',
-      'filesystem_config.txt')
+  filesystem_config_txt = os.path.join(output_target_files_temp_dir, 'META',
+                                       'filesystem_config.txt')
 
   with open(filesystem_config_txt, 'a') as f:
     # TODO(bpeckham) this data is hard coded. It should be generated
     # programmatically.
-    f.write(
-        'system/bin/install-recovery.sh 0 0 750 '
-        'selabel=u:object_r:install_recovery_exec:s0 capabilities=0x0\n')
-    f.write(
-        'system/recovery-from-boot.p 0 0 644 '
-        'selabel=u:object_r:system_file:s0 capabilities=0x0\n')
-    f.write(
-        'system/etc/recovery.img 0 0 440 '
-        'selabel=u:object_r:install_recovery_exec:s0 capabilities=0x0\n')
+    f.write('system/bin/install-recovery.sh 0 0 750 '
+            'selabel=u:object_r:install_recovery_exec:s0 capabilities=0x0\n')
+    f.write('system/recovery-from-boot.p 0 0 644 '
+            'selabel=u:object_r:system_file:s0 capabilities=0x0\n')
+    f.write('system/etc/recovery.img 0 0 440 '
+            'selabel=u:object_r:install_recovery_exec:s0 capabilities=0x0\n')
 
 
-def process_misc_info_txt(
-    system_target_files_temp_dir,
-    other_target_files_temp_dir,
-    output_target_files_temp_dir,
-    system_misc_info_keys):
-  """Perform special processing for META/misc_info.txt
+def process_misc_info_txt(system_target_files_temp_dir,
+                          other_target_files_temp_dir,
+                          output_target_files_temp_dir, system_misc_info_keys):
+  """Perform special processing for META/misc_info.txt.
 
   This function merges the contents of the META/misc_info.txt files from the
   system directory and the other directory, placing the merged result in the
@@ -392,18 +376,15 @@
   content.
 
   Args:
-    system_target_files_temp_dir: The name of a directory containing the
-    special items extracted from the system target files package.
-
-    other_target_files_temp_dir: The name of a directory containing the
-    special items extracted from the other target files package.
-
-    output_target_files_temp_dir: The name of a directory that will be used
-    to create the output target files package after all the special cases
-    are processed.
-
-    system_misc_info_keys: A list of keys to obtain from the system instance
-    of META/misc_info.txt. The remaining keys from the other instance.
+    system_target_files_temp_dir: The name of a directory containing the special
+      items extracted from the system target files package.
+    other_target_files_temp_dir: The name of a directory containing the special
+      items extracted from the other target files package.
+    output_target_files_temp_dir: The name of a directory that will be used to
+      create the output target files package after all the special cases are
+      processed.
+    system_misc_info_keys: A list of keys to obtain from the system instance of
+      META/misc_info.txt. The remaining keys from the other instance.
   """
 
   def read_helper(d):
@@ -434,19 +415,18 @@
     # Partition groups and group sizes are defined by the other (non-system)
     # misc info file because these values may vary for each board that uses
     # a shared system image.
-    for partition_group in merged_info_dict['super_partition_groups'].split(' '):
+    for partition_group in merged_info_dict['super_partition_groups'].split(
+        ' '):
       if ('super_%s_group_size' % partition_group) not in merged_info_dict:
         raise ValueError(
             'Other META/misc_info.txt does not contain required key '
             'super_%s_group_size.' % partition_group)
       key = 'super_%s_partition_list' % partition_group
-      merged_info_dict[key] = '%s %s' % (
-        system_info_dict.get(key, ''),
-        merged_info_dict.get(key, ''))
+      merged_info_dict[key] = '%s %s' % (system_info_dict.get(
+          key, ''), merged_info_dict.get(key, ''))
 
-  output_misc_info_txt = os.path.join(
-      output_target_files_temp_dir,
-      'META', 'misc_info.txt')
+  output_misc_info_txt = os.path.join(output_target_files_temp_dir, 'META',
+                                      'misc_info.txt')
 
   sorted_keys = sorted(merged_info_dict.keys())
 
@@ -464,12 +444,11 @@
 
   Args:
     temp_dir: The name of a scratch directory that this function can use for
-    intermediate files generated during processing.
-
+      intermediate files generated during processing.
     output_target_files_temp_dir: The name of the working directory that must
-    already contain plat_file_contexts and vendor_file_contexts (in the
-    appropriate sub directories), and to which META/file_contexts.bin will be
-    written.
+      already contain plat_file_contexts and vendor_file_contexts (in the
+      appropriate sub directories), and to which META/file_contexts.bin will be
+      written.
   """
 
   # To create a merged file_contexts.bin file, we use the system and vendor
@@ -490,9 +469,8 @@
   for partition in ['SYSTEM', 'VENDOR', 'PRODUCT', 'ODM']:
     prefix = 'plat' if partition == 'SYSTEM' else partition.lower()
 
-    file_contexts = os.path.join(
-        output_target_files_temp_dir,
-        partition, 'etc', 'selinux', prefix + '_file_contexts')
+    file_contexts = os.path.join(output_target_files_temp_dir, partition, 'etc',
+                                 'selinux', prefix + '_file_contexts')
 
     mandatory = partition in ['SYSTEM', 'VENDOR']
 
@@ -518,27 +496,23 @@
 
   # Finally, the compile step creates the final META/file_contexts.bin.
 
-  file_contexts_bin = os.path.join(
-      output_target_files_temp_dir,
-      'META', 'file_contexts.bin')
+  file_contexts_bin = os.path.join(output_target_files_temp_dir, 'META',
+                                   'file_contexts.bin')
 
   command = [
       'sefcontext_compile',
-      '-o', file_contexts_bin,
+      '-o',
+      file_contexts_bin,
       sorted_file_contexts_txt,
   ]
 
   common.RunAndWait(command, verbose=True)
 
 
-def process_special_cases(
-    temp_dir,
-    system_target_files_temp_dir,
-    other_target_files_temp_dir,
-    output_target_files_temp_dir,
-    system_misc_info_keys,
-    rebuild_recovery
-):
+def process_special_cases(temp_dir, system_target_files_temp_dir,
+                          other_target_files_temp_dir,
+                          output_target_files_temp_dir, system_misc_info_keys,
+                          rebuild_recovery):
   """Perform special-case processing for certain target files items.
 
   Certain files in the output target files package require special-case
@@ -546,23 +520,18 @@
 
   Args:
     temp_dir: The name of a scratch directory that this function can use for
-    intermediate files generated during processing.
-
-    system_target_files_temp_dir: The name of a directory containing the
-    special items extracted from the system target files package.
-
-    other_target_files_temp_dir: The name of a directory containing the
-    special items extracted from the other target files package.
-
-    output_target_files_temp_dir: The name of a directory that will be used
-    to create the output target files package after all the special cases
-    are processed.
-
-    system_misc_info_keys: A list of keys to obtain from the system instance
-    of META/misc_info.txt. The remaining keys from the other instance.
-
+      intermediate files generated during processing.
+    system_target_files_temp_dir: The name of a directory containing the special
+      items extracted from the system target files package.
+    other_target_files_temp_dir: The name of a directory containing the special
+      items extracted from the other target files package.
+    output_target_files_temp_dir: The name of a directory that will be used to
+      create the output target files package after all the special cases are
+      processed.
+    system_misc_info_keys: A list of keys to obtain from the system instance of
+      META/misc_info.txt. The remaining keys from the other instance.
     rebuild_recovery: If true, rebuild the recovery patch used by non-A/B
-    devices and write it to the system image.
+      devices and write it to the system image.
   """
 
   if 'ab_update' in system_misc_info_keys:
@@ -586,19 +555,11 @@
       output_target_files_temp_dir=output_target_files_temp_dir)
 
 
-def merge_target_files(
-    temp_dir,
-    system_target_files,
-    system_item_list,
-    system_misc_info_keys,
-    other_target_files,
-    other_item_list,
-    output_target_files,
-    output_dir,
-    output_item_list,
-    output_ota,
-    output_super_empty,
-    rebuild_recovery):
+def merge_target_files(temp_dir, system_target_files, system_item_list,
+                       system_misc_info_keys, other_target_files,
+                       other_item_list, output_target_files, output_dir,
+                       output_item_list, output_ota, output_super_empty,
+                       rebuild_recovery):
   """Merge two target files packages together.
 
   This function takes system and other target files packages as input, performs
@@ -607,45 +568,35 @@
 
   Args:
     temp_dir: The name of a directory we use when we extract items from the
-    input target files packages, and also a scratch directory that we use for
-    temporary files.
-
+      input target files packages, and also a scratch directory that we use for
+      temporary files.
     system_target_files: The name of the zip archive containing the system
-    partial target files package.
-
+      partial target files package.
     system_item_list: The list of items to extract from the partial system
-    target files package as is, meaning these items will land in the output
-    target files package exactly as they appear in the input partial system
-    target files package.
-
+      target files package as is, meaning these items will land in the output
+      target files package exactly as they appear in the input partial system
+      target files package.
     system_misc_info_keys: The list of keys to obtain from the system instance
-    of META/misc_info.txt. The remaining keys from the other instance.
-
-    other_target_files: The name of the zip archive containing the other
-    partial target files package.
-
-    other_item_list: The list of items to extract from the partial other
-    target files package as is, meaning these items will land in the output
-    target files package exactly as they appear in the input partial other
-    target files package.
-
-    output_target_files: The name of the output zip archive target files
-    package created by merging system and other.
-
+      of META/misc_info.txt. The remaining keys from the other instance.
+    other_target_files: The name of the zip archive containing the other partial
+      target files package.
+    other_item_list: The list of items to extract from the partial other target
+      files package as is, meaning these items will land in the output target
+      files package exactly as they appear in the input partial other target
+      files package.
+    output_target_files: The name of the output zip archive target files package
+      created by merging system and other.
+    output_dir: The destination directory for saving merged files.
+    output_item_list: The list of items to copy into the output_dir.
     output_ota: The name of the output zip archive ota package.
-
     output_super_empty: If provided, creates a super_empty.img file from the
-    merged target files package and saves it at this path.
-
+      merged target files package and saves it at this path.
     rebuild_recovery: If true, rebuild the recovery patch used by non-A/B
-    devices and write it to the system image.
+      devices and write it to the system image.
   """
 
-  logger.info(
-      'starting: merge system %s and other %s into output %s',
-      system_target_files,
-      other_target_files,
-      output_target_files)
+  logger.info('starting: merge system %s and other %s into output %s',
+              system_target_files, other_target_files, output_target_files)
 
   # Create directory names that we'll use when we extract files from system,
   # and other, and for zipping the final output.
@@ -706,8 +657,9 @@
   # Create super_empty.img using the merged misc_info.txt.
 
   if output_super_empty:
-    misc_info_txt = os.path.join(output_target_files_temp_dir,
-                                 'META', 'misc_info.txt')
+    misc_info_txt = os.path.join(output_target_files_temp_dir, 'META',
+                                 'misc_info.txt')
+
     def read_helper():
       with open(misc_info_txt) as f:
         return list(f.read().splitlines())
@@ -718,9 +670,9 @@
           'Building super_empty.img requires use_dynamic_partitions=true.')
 
     build_super_image_args = [
-      '--verbose',
-      misc_info_txt,
-      output_super_empty,
+        '--verbose',
+        misc_info_txt,
+        output_super_empty,
     ]
     build_super_image.main(build_super_image_args)
 
@@ -744,8 +696,8 @@
 
   output_zip = os.path.abspath(output_target_files)
   output_target_files_list = os.path.join(temp_dir, 'output.list')
-  output_target_files_meta_dir = os.path.join(
-      output_target_files_temp_dir, 'META')
+  output_target_files_meta_dir = os.path.join(output_target_files_temp_dir,
+                                              'META')
 
   command = [
       'find',
@@ -754,13 +706,8 @@
   # TODO(bpeckham): sort this to be more like build.
   meta_content = common.RunAndCheckOutput(command, verbose=False)
   command = [
-      'find',
-      output_target_files_temp_dir,
-      '-path',
-      output_target_files_meta_dir,
-      '-prune',
-      '-o',
-      '-print'
+      'find', output_target_files_temp_dir, '-path',
+      output_target_files_meta_dir, '-prune', '-o', '-print'
   ]
   # TODO(bpeckham): sort this to be more like build.
   other_content = common.RunAndCheckOutput(command, verbose=False)
@@ -772,9 +719,12 @@
   command = [
       'soong_zip',
       '-d',
-      '-o', output_zip,
-      '-C', output_target_files_temp_dir,
-      '-l', output_target_files_list,
+      '-o',
+      output_zip,
+      '-C',
+      output_target_files_temp_dir,
+      '-l',
+      output_target_files_list,
   ]
   logger.info('creating %s', output_target_files)
   common.RunAndWait(command, verbose=True)
@@ -796,9 +746,8 @@
   directory. It also cleans up the temporary directory.
 
   Args:
-    func: The function to call. Should accept one parameter, the path to
-    the temporary directory.
-
+    func: The function to call. Should accept one parameter, the path to the
+      temporary directory.
     keep_tmp: Keep the temporary directory after processing is complete.
   """
 
@@ -858,7 +807,8 @@
     return True
 
   args = common.ParseOptions(
-      sys.argv[1:], __doc__,
+      sys.argv[1:],
+      __doc__,
       extra_long_opts=[
           'system-target-files=',
           'system-item-list=',
@@ -875,13 +825,10 @@
       ],
       extra_option_handler=option_handler)
 
-  if (len(args) != 0 or
-      OPTIONS.system_target_files is None or
-      OPTIONS.other_target_files is None or (
-        OPTIONS.output_target_files is None and
-        OPTIONS.output_dir is None) or (
-        OPTIONS.output_dir is not None and
-        OPTIONS.output_item_list is None)):
+  if (args or OPTIONS.system_target_files is None or
+      OPTIONS.other_target_files is None or
+      (OPTIONS.output_target_files is None and OPTIONS.output_dir is None) or
+      (OPTIONS.output_dir is not None and OPTIONS.output_item_list is None)):
     common.Usage(__doc__)
     sys.exit(1)
 
@@ -924,8 +871,7 @@
           output_item_list=output_item_list,
           output_ota=OPTIONS.output_ota,
           output_super_empty=OPTIONS.output_super_empty,
-          rebuild_recovery=OPTIONS.rebuild_recovery),
-      OPTIONS.keep_tmp)
+          rebuild_recovery=OPTIONS.rebuild_recovery), OPTIONS.keep_tmp)
 
 
 if __name__ == '__main__':