blimp: Update page load status update indicator to use first paint.

cc/trees/remote_channel_main.cc

Index: cc/trees/remote_channel_main.cc
diff --git a/cc/trees/remote_channel_main.cc b/cc/trees/remote_channel_main.cc
index a231bcbe061dde24317cbce8969b914dde928e2f..70da4f3faba81ea81e9d7be6c44343d1d148b741 100644
--- a/cc/trees/remote_channel_main.cc
+++ b/cc/trees/remote_channel_main.cc
@@ -177,13 +177,18 @@ void RemoteChannelMain::StartCommitOnImpl(
   to_impl_proto->set_message_type(proto::CompositorMessageToImpl::START_COMMIT);
   proto::StartCommit* start_commit_message =
       to_impl_proto->mutable_start_commit_message();
+  std::vector<std::unique_ptr<SwapPromise>> swap_promises;
   layer_tree_host->ToProtobufForCommit(
-      start_commit_message->mutable_layer_tree_host());
+      start_commit_message->mutable_layer_tree_host(), &swap_promises);
 
   VLOG(1) << "Sending commit message to client. Commit bytes size: "
           << proto.ByteSize();
   SendMessageProto(proto);
 
+  // Activate the swap promises after the commit is queued.

[vmpstr, 2016/05/18 18:05:59]

Can you expand the comment to explain why this is necessary?

[Khushal, 2016/05/18 21:16:58]

Sure, Done.

+  for (const auto& swap_promise : swap_promises)
+    swap_promise->DidActivate();
+
   // In order to avoid incurring the overhead for the client to send us a
   // message for when a frame to be committed is drawn we inform the embedder
   // that the draw was successful immediately after sending the commit message.