Add a bunch of vlogs to RAF related calls in chrome.

content/renderer/gpu/render_widget_compositor.cc

Index: content/renderer/gpu/render_widget_compositor.cc
diff --git a/content/renderer/gpu/render_widget_compositor.cc b/content/renderer/gpu/render_widget_compositor.cc
index e1023d294d5be15694b21acd51dda83bc55deebb..b0931771d4afc8706a6eac1a17a5451f2cf13c6c 100644
--- a/content/renderer/gpu/render_widget_compositor.cc
+++ b/content/renderer/gpu/render_widget_compositor.cc
@@ -756,6 +756,7 @@ void RenderWidgetCompositor::DidBeginMainFrame() {
 }
 
 void RenderWidgetCompositor::BeginMainFrame(const cc::BeginFrameArgs& args) {
+  VLOG(2) << "RenderWidgetCompositor::BeginMainFrame";
   begin_main_frame_time_ = args.frame_time;
   begin_main_frame_interval_ = args.interval;
   double frame_time = (args.frame_time - base::TimeTicks()).InSecondsF();