Delay activation/draw on GPU tile work completion

cc/raster/gpu_raster_buffer_provider.cc

Index: cc/raster/gpu_raster_buffer_provider.cc
diff --git a/cc/raster/gpu_raster_buffer_provider.cc b/cc/raster/gpu_raster_buffer_provider.cc
index e7e4f9200ad100c02c050b101cf3b22872ec4fb7..500b761f7db69d7d43f2ba2b14466f08be1eca2c 100644
--- a/cc/raster/gpu_raster_buffer_provider.cc
+++ b/cc/raster/gpu_raster_buffer_provider.cc
@@ -17,6 +17,7 @@
 #include "cc/playback/raster_source.h"
 #include "cc/raster/scoped_gpu_raster.h"
 #include "cc/resources/resource.h"
+#include "gpu/command_buffer/client/context_support.h"
 #include "gpu/command_buffer/client/gles2_interface.h"
 #include "third_party/skia/include/core/SkMultiPictureDraw.h"
 #include "third_party/skia/include/core/SkPictureRecorder.h"
@@ -186,6 +187,44 @@ bool GpuRasterBufferProvider::CanPartialRasterIntoProvidedResource() const {
   return msaa_sample_count_ == 0;
 }
 
+bool GpuRasterBufferProvider::IsResourceReadyToDraw(
+    ResourceId resource_id) const {
+  if (!async_worker_context_enabled_)
+    return true;
+
+  gpu::SyncToken sync_token =
+      resource_provider_->GetSyncTokenForResource(resource_id);
+  if (!sync_token.HasData())
+    return true;
+
+  // IsSyncTokenSignalled is threadsafe, no need for worker context lock.
+  return worker_context_provider_->ContextSupport()->IsSyncTokenSignalled(
+      sync_token);
+}
+
+uint64_t GpuRasterBufferProvider::SetReadyToDrawCallback(
+    const ResourceProvider::ResourceIdArray& resource_ids,
+    const base::Closure& callback,
+    uint64_t pending_callback_id) const {
+  if (!async_worker_context_enabled_)
+    return 0;
+
+  gpu::SyncToken sync_token =
+      resource_provider_->GetSyncTokenForResources(resource_ids);
+  uint64_t callback_id = sync_token.release_count();
+  DCHECK_NE(callback_id, 0u);
+
+  // If the callback we are about to request has the same ID as the one which

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

It's a bit awkward that this comment is talking about the "else" case. I think
it's fine, but maybe rephrase it as "If callback_id is different, then ...;
Otherwise, the request is redundant"

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

Done.

+  // our caller is waiting on, then the request is redundant.
+  if (callback_id != pending_callback_id) {
+    // SignalSyncToken is threadsafe, no need for worker context lock.
+    worker_context_provider_->ContextSupport()->SignalSyncToken(sync_token,
+                                                                callback);
+  }
+
+  return callback_id;
+}
+
 void GpuRasterBufferProvider::Shutdown() {
   pending_raster_buffers_.clear();
 }