Make RenderViewImpl::OnForceRedraw more robust

cc/trees/layer_tree_host_impl.cc

Index: cc/trees/layer_tree_host_impl.cc
diff --git a/cc/trees/layer_tree_host_impl.cc b/cc/trees/layer_tree_host_impl.cc
index 77a44b6700d7c8eec52d93e61e40621bb1f4023c..74746f457fd54f05d96b45f8a71a105fc50d8a59 100644
--- a/cc/trees/layer_tree_host_impl.cc
+++ b/cc/trees/layer_tree_host_impl.cc
@@ -628,6 +628,11 @@ void LayerTreeHostImpl::QueueSwapPromiseForMainThreadScrollUpdate(
       std::move(swap_promise));
 }
 
+void LayerTreeHostImpl::QueueForcedRedrawSwapPromise(
+    std::unique_ptr<SwapPromise> swap_promise) {
+  forced_redraw_swap_promises_.push_back(std::move(swap_promise));

[piman, 2016/07/28 20:54:09]

This would bypass the activation, meaning, you may end up calling DidSwap before
you actually drew the frame you forced.

+}
+
 void LayerTreeHostImpl::TrackDamageForAllSurfaces(
     const LayerImplList& render_surface_layer_list) {
   // For now, we use damage tracking to compute a global scissor. To do this, we
@@ -1839,6 +1844,12 @@ bool LayerTreeHostImpl::SwapBuffers(const LayerTreeHostImpl::FrameData& frame) {
                                0, 0);
     }
   }
+
+  for (const auto& promise : forced_redraw_swap_promises_) {
+    promise->DidSwap(&metadata);
+  }
+  forced_redraw_swap_promises_.clear();
+
   renderer_->SwapBuffers(std::move(metadata));
   return true;
 }