WIP GPU scheduler + delayed activation / tile draw

cc/raster/zero_copy_raster_buffer_provider.h

Index: cc/raster/zero_copy_raster_buffer_provider.h
diff --git a/cc/raster/zero_copy_raster_buffer_provider.h b/cc/raster/zero_copy_raster_buffer_provider.h
index 6abf129d73d6ff630a48fb991d73cac8ec2bc5d4..baa28d6db79e55950d6ede0604943e13d814105a 100644
--- a/cc/raster/zero_copy_raster_buffer_provider.h
+++ b/cc/raster/zero_copy_raster_buffer_provider.h
@@ -36,6 +36,9 @@ class CC_EXPORT ZeroCopyRasterBufferProvider : public RasterBufferProvider {
       uint64_t previous_content_id) override;
   void ReleaseBufferForRaster(std::unique_ptr<RasterBuffer> buffer) override;
   void OrderingBarrier() override;
+  bool IsResourceReadyToDraw(const Resource* resource) override;
+  void SignalResourcesReadyToDraw(const std::vector<const Resource*>& resources,
+                                  const base::Closure& callback) override;
   ResourceFormat GetResourceFormat(bool must_support_alpha) const override;
   bool IsResourceSwizzleRequired(bool must_support_alpha) const override;
   bool CanPartialRasterIntoProvidedResource() const override;