Allow Blink to generate cc::FrameSinkId from RenderThread

third_party/WebKit/public/platform/Platform.h

Index: third_party/WebKit/public/platform/Platform.h
diff --git a/third_party/WebKit/public/platform/Platform.h b/third_party/WebKit/public/platform/Platform.h
index 747885a940b479fac6bcd5a2f069c40775d78f50..e8e786ffcf145627955cdb4bc791ca4cebfaca5c 100644
--- a/third_party/WebKit/public/platform/Platform.h
+++ b/third_party/WebKit/public/platform/Platform.h
@@ -55,6 +55,7 @@
 #include "WebVector.h"
 #include "base/metrics/user_metrics_action.h"
 #include "cc/resources/shared_bitmap.h"
+#include "cc/surfaces/frame_sink_id.h"
 
 class GrContext;
 
@@ -321,6 +322,9 @@ class BLINK_PLATFORM_EXPORT Platform {
   // the process's process ID.
   virtual uint32_t getUniqueIdForProcess() { return 0; }
 
+  // Returns a unique FrameSinkID for the current renderer process
+  virtual cc::FrameSinkId generateFrameSinkId() { return cc::FrameSinkId(); }
+
   // Message Ports -------------------------------------------------------
 
   // Creates a Message Port Channel pair. This can be called on any thread.