AU: Verify that the applied delta update matches the server-sent hashes.

Also, don't try to resume any delta update that fails for any reason
other than download transfer errors.

BUG=7348
TEST=unit tests, gmerged on device

Change-Id: Ice464b8d421256717d7909fd5fa46d762bd48952

Review URL: http://codereview.chromium.org/3599025
diff --git a/delta_performer_unittest.cc b/delta_performer_unittest.cc
index b8d6554..a3c43f6 100755
--- a/delta_performer_unittest.cc
+++ b/delta_performer_unittest.cc
@@ -286,6 +286,7 @@
   EXPECT_EQ(0, performer.Close());
 
   CompareFilesByBlock(old_kernel, new_kernel);
+  CompareFilesByBlock(a_img, b_img);
 
   vector<char> updated_kernel_partition;
   EXPECT_TRUE(utils::ReadFile(old_kernel, &updated_kernel_partition));
@@ -297,6 +298,7 @@
       kUnittestPublicKeyPath,
       OmahaHashCalculator::OmahaHashOfData(delta),
       delta.size()));
+  EXPECT_TRUE(performer.VerifyAppliedUpdate(a_img, old_kernel));
 }
 
 TEST(DeltaPerformerTest, NewFullUpdateTest) {