Centralize FrameSinkId allocation in one place

android_webview/browser/surfaces_instance.h

Index: android_webview/browser/surfaces_instance.h
diff --git a/android_webview/browser/surfaces_instance.h b/android_webview/browser/surfaces_instance.h
index ab5cf1a4683e169fb5df7153c7e53b8c29bf7922..0eaf98555ac53ea7e0b3301f651ed27aecd46859 100644
--- a/android_webview/browser/surfaces_instance.h
+++ b/android_webview/browser/surfaces_instance.h
@@ -12,6 +12,7 @@
 #include "cc/surfaces/compositor_frame_sink_support_client.h"
 #include "cc/surfaces/display_client.h"
 #include "cc/surfaces/frame_sink_id.h"
+#include "cc/surfaces/frame_sink_id_allocator.h"
 #include "cc/surfaces/surface_id.h"
 
 namespace cc {
@@ -72,7 +73,7 @@ class SurfacesInstance : public base::RefCounted<SurfacesInstance>,
 
   void SetEmptyRootFrame();
 
-  uint32_t next_client_id_;
+  cc::FrameSinkIdAllocator frame_sink_id_allocator_;
 
   cc::FrameSinkId frame_sink_id_;