Use kRenderClientId command line flag when starting a render process

content/renderer/render_widget.cc

Index: content/renderer/render_widget.cc
diff --git a/content/renderer/render_widget.cc b/content/renderer/render_widget.cc
index 57bb2085f61e3f419307f96fb827956bc7ba7206..03b38ffe148ce51698f411d701897edca4e1cff4 100644
--- a/content/renderer/render_widget.cc
+++ b/content/renderer/render_widget.cc
@@ -247,6 +247,13 @@ RenderWidget::RenderWidget(CompositorDependencies* compositor_deps,
       text_input_client_observer_(new TextInputClientObserver(this)),
 #endif
       focused_pepper_plugin_(nullptr) {
+  if (base::CommandLine::ForCurrentProcess()->HasSwitch(

[Fady Samuel, 2016/10/27 20:15:55]

I see no point in saving this here. 

[Alex Z., 2016/10/28 18:09:47]

Done.

+          switches::kRendererClientId)) {
+    std::string client_id_str =
+        base::CommandLine::ForCurrentProcess()->GetSwitchValueASCII(
+            switches::kRendererClientId);
+    client_id_ = std::stoi(client_id_str);
+  }
   if (!swapped_out)
     RenderProcess::current()->AddRefProcess();
   DCHECK(RenderThread::Get());
@@ -365,6 +372,8 @@ void RenderWidget::SetRoutingID(int32_t routing_id) {
   routing_id_ = routing_id;
   input_handler_.reset(new RenderWidgetInputHandler(
       GetRenderWidgetInputHandlerDelegate(this), this));
+
+  OnSetFrameSinkId(cc::FrameSinkId(client_id_, routing_id_));

[Fady Samuel, 2016/10/27 20:15:55]

I don't believe we have a RenderWidgetCompositor yet at this point. We should
just get rid of OnSetFrameSinkId and the chrome IPC.

[Alex Z., 2016/10/28 18:09:47]

Done.

 }
 
 void RenderWidget::SetSwappedOut(bool is_swapped_out) {
@@ -1114,6 +1123,7 @@ void RenderWidget::initializeLayerTreeView() {
     compositor_->SetNeverVisible();
 
   StartCompositor();
+  compositor_->SetFrameSinkId(cc::FrameSinkId(client_id_, routing_id_));

[Fady Samuel, 2016/10/27 20:15:55]

We can simply read the client id from commandline here.

[Alex Z., 2016/10/28 18:09:47]

Done.

 }
 
 void RenderWidget::WillCloseLayerTreeView() {