[DevTools] Remove WebDevToolsAgent::setLayerTreeId calls.

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 1835121df0d180053a0ccf3d88218f6cb70dce8e..13a493da222a2431013a49de486274363c911ef3 100644
--- a/content/renderer/gpu/render_widget_compositor.cc
+++ b/content/renderer/gpu/render_widget_compositor.cc
@@ -528,10 +528,6 @@ void RenderWidgetCompositor::QueueSwapPromise(
   layer_tree_host_->QueueSwapPromise(swap_promise.Pass());
 }
 
-int RenderWidgetCompositor::GetLayerTreeId() const {
-  return layer_tree_host_->id();
-}
-
 int RenderWidgetCompositor::GetSourceFrameNumber() const {
   return layer_tree_host_->source_frame_number();
 }