content: Rename raster threads to worker threads.

cc/test/test_task_graph_runner.cc

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/test/test_task_graph_runner.h"
 
 namespace cc {
 
-TestTaskGraphRunner::TestTaskGraphRunner()
-    : worker_thread_(this, "CompositorTileWorker1") {
+TestTaskGraphRunner::TestTaskGraphRunner() : worker_thread_(this, "Worker1") {
   worker_thread_.Start();
 }
 
 TestTaskGraphRunner::~TestTaskGraphRunner() {
   TaskGraphRunner::Shutdown();
   worker_thread_.Join();
 }
 
 void TestTaskGraphRunner::Run() {
   TaskGraphRunner::Run();
 }
 
 }  // namespace cc