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

download_action.cc

Index: download_action.cc
diff --git a/download_action.cc b/download_action.cc
index b88e44825a3644d4b593838c387d128947a40d8a..2920d16fd055503097f7d8695be389a44bd55c79 100644
--- a/download_action.cc
+++ b/download_action.cc
@@ -147,6 +147,11 @@ void DownloadAction::TransferComplete(HttpFetcher *fetcher, bool successful) {
         LOG(ERROR) << "Download of " << install_plan_.download_url
                    << " failed due to payload verification error.";
         code = kActionCodeDownloadPayloadVerificationError;
+      } else if (!delta_performer_->VerifyAppliedUpdate(
+          install_plan_.install_path, install_plan_.kernel_install_path)) {
+        LOG(ERROR) << "Download of " << install_plan_.download_url
+                   << " failed due to applied update verification error.";
+        code = kActionCodeDownloadAppliedUpdateVerificationError;
       }
     } else {
       // Makes sure the hash and size are correct for an old-style full update.