cc: Remove ScheduleOnOriginThread() and CompleteOnOriginThread().

cc/raster/zero_copy_tile_task_worker_pool.cc

Index: cc/raster/zero_copy_tile_task_worker_pool.cc
diff --git a/cc/raster/zero_copy_tile_task_worker_pool.cc b/cc/raster/zero_copy_tile_task_worker_pool.cc
index 203415a7c5d22abf23e28030ee8c4770f22b0643..e4f75b37d0d226f6e3bfde22eab9c15f06b65814 100644
--- a/cc/raster/zero_copy_tile_task_worker_pool.cc
+++ b/cc/raster/zero_copy_tile_task_worker_pool.cc
@@ -105,24 +105,14 @@ void ZeroCopyTileTaskWorkerPool::Shutdown() {
 void ZeroCopyTileTaskWorkerPool::ScheduleTasks(TaskGraph* graph) {
   TRACE_EVENT0("cc", "ZeroCopyTileTaskWorkerPool::ScheduleTasks");
 
-  ScheduleTasksOnOriginThread(this, graph);
   task_graph_runner_->ScheduleTasks(namespace_token_, graph);
 }
 
-void ZeroCopyTileTaskWorkerPool::CheckForCompletedTasks() {
+void ZeroCopyTileTaskWorkerPool::CollectCompletedTasks(
+    Task::Vector* completed_tasks) {
   TRACE_EVENT0("cc", "ZeroCopyTileTaskWorkerPool::CheckForCompletedTasks");
 
-  task_graph_runner_->CollectCompletedTasks(namespace_token_,
-                                            &completed_tasks_);
-  for (Task::Vector::const_iterator it = completed_tasks_.begin();
-       it != completed_tasks_.end(); ++it) {
-    TileTask* task = static_cast<TileTask*>(it->get());
-
-    task->WillComplete();
-    task->CompleteOnOriginThread(this);
-    task->DidComplete();
-  }
-  completed_tasks_.clear();
+  task_graph_runner_->CollectCompletedTasks(namespace_token_, completed_tasks);
 }
 
 ResourceFormat ZeroCopyTileTaskWorkerPool::GetResourceFormat(
@@ -141,6 +131,10 @@ bool ZeroCopyTileTaskWorkerPool::GetResourceRequiresSwizzle(
   return ResourceFormatRequiresSwizzle(GetResourceFormat(must_support_alpha));
 }
 
+TileTaskClient* ZeroCopyTileTaskWorkerPool::AsTileTaskClient() {
+  return this;
+}
+
 std::unique_ptr<RasterBuffer>
 ZeroCopyTileTaskWorkerPool::AcquireBufferForRaster(
     const Resource* resource,