Centralize FrameSinkId allocation in one place

content/browser/renderer_host/render_widget_host_impl.h

Index: content/browser/renderer_host/render_widget_host_impl.h
diff --git a/content/browser/renderer_host/render_widget_host_impl.h b/content/browser/renderer_host/render_widget_host_impl.h
index 1db87d02d17328e6be174c4b676781e7b464d405..8d83000306a4d24a77fd36aae39cc14c6f334a09 100644
--- a/content/browser/renderer_host/render_widget_host_impl.h
+++ b/content/browser/renderer_host/render_widget_host_impl.h
@@ -25,6 +25,7 @@
 #include "base/timer/elapsed_timer.h"
 #include "build/build_config.h"
 #include "cc/resources/shared_bitmap.h"
+#include "cc/surfaces/frame_sink_id.h"
 #include "content/browser/renderer_host/event_with_latency_info.h"
 #include "content/browser/renderer_host/input/input_ack_handler.h"
 #include "content/browser/renderer_host/input/input_router_client.h"
@@ -135,6 +136,8 @@ class CONTENT_EXPORT RenderWidgetHostImpl : public RenderWidgetHost,
 
   RenderWidgetHostOwnerDelegate* owner_delegate() { return owner_delegate_; }
 
+  cc::FrameSinkId AllocateFrameSinkId(bool is_guest_view_hack);
+
   // RenderWidgetHost implementation.
   void UpdateTextDirection(blink::WebTextDirection direction) override;
   void NotifyTextDirection() override;