Add preliminary support for hw-accelerated tile rasterization.

cc/resources/pixel_buffer_raster_worker_pool.cc

Index: cc/resources/pixel_buffer_raster_worker_pool.cc
diff --git a/cc/resources/pixel_buffer_raster_worker_pool.cc b/cc/resources/pixel_buffer_raster_worker_pool.cc
index 011e5147e066e4c3e294aceb14ae22bc0b931f31..9a3070dab592a663a99f328aa30e20c24f59f859 100644
--- a/cc/resources/pixel_buffer_raster_worker_pool.cc
+++ b/cc/resources/pixel_buffer_raster_worker_pool.cc
@@ -91,9 +91,10 @@ bool WasCanceled(const internal::RasterWorkerPoolTask* task) {
 
 PixelBufferRasterWorkerPool::PixelBufferRasterWorkerPool(
     ResourceProvider* resource_provider,
+    ContextProvider* context_provider,
     size_t num_threads,
     size_t max_transfer_buffer_usage_bytes)
-    : RasterWorkerPool(resource_provider, num_threads),
+    : RasterWorkerPool(resource_provider, context_provider, num_threads),
       shutdown_(false),
       scheduled_raster_task_count_(0),
       bytes_pending_upload_(0),
@@ -137,6 +138,7 @@ void PixelBufferRasterWorkerPool::Shutdown() {
 void PixelBufferRasterWorkerPool::ScheduleTasks(RasterTask::Queue* queue) {
   TRACE_EVENT0("cc", "PixelBufferRasterWorkerPool::ScheduleTasks");
 
+  RasterWorkerPool::CompleteOriginThreadTasks(queue);

[reveman, 2013/12/17 00:28:48]

Should we call this after ScheduleCheckForCompletedRasterTasks()? That would
allow worker threads and uploads to run at the same time.

[alokp, 2013/12/17 22:12:15]

Done.

   RasterWorkerPool::SetRasterTasks(queue);
 
   if (!should_notify_client_if_no_tasks_are_pending_)