Add LayerTreeHostClient::{will,did}UpdateLayer, report layer updates to DevTools

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 ca7a37fa8b1baaa635a00c27b21c0da51a008480..c361538372dd1916ce5aaf02630393ba908364ac 100644
--- a/content/renderer/gpu/render_widget_compositor.cc
+++ b/content/renderer/gpu/render_widget_compositor.cc
@@ -357,6 +357,10 @@ void RenderWidgetCompositor::SetLatencyInfo(
   layer_tree_host_->SetLatencyInfo(latency_info);
 }
 
+int RenderWidgetCompositor::GetLayerTreeId() const {
+  return layer_tree_host_->id();
+}
+
 bool RenderWidgetCompositor::initialize(cc::LayerTreeSettings settings) {
   scoped_refptr<base::MessageLoopProxy> compositor_message_loop_proxy =
       RenderThreadImpl::current()->compositor_message_loop_proxy();