cc: Trace the viewport size changing.

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 53eb58bb0c4a19007d295abd92a9db09fcff7201..fb49e32889b9f8f283e7e97a10ee7e3b72ffc1e4 100644
--- a/cc/trees/layer_tree_host_impl.cc
+++ b/cc/trees/layer_tree_host_impl.cc
@@ -2198,6 +2198,9 @@ void LayerTreeHostImpl::ReleaseGL() {
 void LayerTreeHostImpl::SetViewportSize(const gfx::Size& device_viewport_size) {
   if (device_viewport_size == device_viewport_size_)
     return;
+  TRACE_EVENT2("cc", "LayerTreeHostImpl::SetViewportSize", "width",

[enne (OOO), 2015/02/05 00:22:25]

TRACE_EVENT_INSTANT_2?

[danakj, 2015/02/05 00:27:12]

Oh, yes. Done.

+               device_viewport_size.width(), "height",
+               device_viewport_size.height());
 
   if (pending_tree_)
     active_tree_->SetViewportSizeInvalid();