WIP GPU scheduler + delayed activation / tile draw

cc/raster/raster_buffer_provider.h

Index: cc/raster/raster_buffer_provider.h
diff --git a/cc/raster/raster_buffer_provider.h b/cc/raster/raster_buffer_provider.h
index 8c3b64473673c34ca7b73f0238cc8fd3462e58de..190966b121e21a780f830ef96c26aa93e2318311 100644
--- a/cc/raster/raster_buffer_provider.h
+++ b/cc/raster/raster_buffer_provider.h
@@ -50,6 +50,12 @@ class CC_EXPORT RasterBufferProvider {
   // Release raster buffer.
   virtual void ReleaseBufferForRaster(std::unique_ptr<RasterBuffer> buffer) = 0;
 
+  virtual bool IsResourceReadyToDraw(const Resource* resource) = 0;
+
+  virtual void SignalResourcesReadyToDraw(
+      const std::vector<const Resource*>& resources,
+      const base::Closure& callback) = 0;
+
   // Used for syncing resources to the worker context.
   virtual void OrderingBarrier() = 0;