Delay activation/draw on GPU tile work completion

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..701fec97f72063c1a458c341da75a0e81e9991d5 100644
--- a/cc/raster/raster_buffer_provider.h
+++ b/cc/raster/raster_buffer_provider.h
@@ -12,6 +12,7 @@
 #include "cc/raster/task_graph_runner.h"
 #include "cc/raster/tile_task.h"
 #include "cc/resources/resource_format.h"
+#include "cc/resources/resource_provider.h"
 #include "ui/gfx/geometry/rect.h"
 #include "ui/gfx/geometry/size.h"
 
@@ -63,6 +64,19 @@ class CC_EXPORT RasterBufferProvider {
   // the Resource provided in AcquireBufferForRaster.
   virtual bool CanPartialRasterIntoProvidedResource() const = 0;
 
+  // Returns true if the indicated resource is ready to draw.
+  virtual bool IsResourceReadyToDraw(ResourceId id) const = 0;
+
+  // Calls the provided |callback| when the provided |resources| are ready to
+  // draw. Returns a callback ID which can be used to track this callback.
+  // Will return 0 if no callback is needed (resources are already ready to
+  // draw). The caller may optionally pass the ID of a pending callback to
+  // avoid creating a new callback unnecessarily.

[vmpstr, 2017/01/05 22:00:46]

Can you specify to pass 0 if no pending callback exists? Also, is this something
that the RasterBufferProvider (or its overrides) can keep track of? That is, it
should know the last callback id it returned, no?

Or is there something more subtle here?

[ericrk, 2017/01/09 23:05:21]

The RasterBufferProvider knows the last callback it returned, but the
TileManager simultaneously requests callbacks for both ready to draw and ready
to activate callbacks - RasterBufferProvider doesn't know the difference between
these so it can't really de-dupe them.

+  virtual uint64_t SetReadyToDrawCallback(
+      const ResourceProvider::ResourceIdArray& resource_ids,
+      const base::Callback<void()>& callback,
+      uint64_t pending_callback_id) const = 0;
+
   // Shutdown for doing cleanup.
   virtual void Shutdown() = 0;