AU: Verify source rootfs/kernel hashes before applying delta.

New style full updates will not send the old rootfs hash so no check takes
place.

BUG=7562
TEST=unit tests, gmerged on device and tested with good/bad source partition

Change-Id: I65b28bf57110e4d87472d4aea59121878cde24b0

Review URL: http://codereview.chromium.org/3712003
diff --git a/delta_diff_generator.cc b/delta_diff_generator.cc
index 9659ad2..f024481 100644
--- a/delta_diff_generator.cc
+++ b/delta_diff_generator.cc
@@ -611,6 +611,7 @@
   TEST_AND_RETURN_FALSE(hasher.Finalize());
   const vector<char>& hash = hasher.raw_hash();
   info->set_hash(hash.data(), hash.size());
+  LOG(INFO) << "hash: " << hasher.hash();
   return true;
 }
 
@@ -619,12 +620,8 @@
                               const string& old_rootfs,
                               const string& new_rootfs,
                               DeltaArchiveManifest* manifest) {
-  if (!old_kernel.empty()) {
-    TEST_AND_RETURN_FALSE(
-        InitializePartitionInfo(true,
-                                old_kernel,
-                                manifest->mutable_old_kernel_info()));
-  }
+  // TODO(petkov): Generate the old kernel info when we stop generating full
+  // updates for the kernel partition.
   TEST_AND_RETURN_FALSE(
       InitializePartitionInfo(true,
                               new_kernel,