Add request tracking.

RequestTracker keeps track of how many buffers are in flight for
each stream, and what frame numbers correspond to what requests/buffers.

BUG: 31044638
TEST: unit tests pass

Change-Id: I8ef3fcacdf8171514ea7f7eaf77301a641bff61e
diff --git a/modules/camera/3_4/Android.mk b/modules/camera/3_4/Android.mk
index 12e8436..1211a08 100644
--- a/modules/camera/3_4/Android.mk
+++ b/modules/camera/3_4/Android.mk
@@ -39,10 +39,12 @@
 
 v4l2_src_files := \
   camera.cpp \
+  capture_request.cpp \
   format_metadata_factory.cpp \
   metadata/enum_converter.cpp \
   metadata/metadata.cpp \
   metadata/metadata_reader.cpp \
+  request_tracker.cpp \
   static_properties.cpp \
   stream.cpp \
   stream_format.cpp \
@@ -70,6 +72,7 @@
   metadata/tagged_control_delegate_test.cpp \
   metadata/tagged_control_options_test.cpp \
   metadata/v4l2_control_delegate_test.cpp \
+  request_tracker_test.cpp \
   static_properties_test.cpp \
 
 # V4L2 Camera HAL.