cc: Make single-thread renderer compositor always synchronous.

cc/trees/layer_tree_host_pixeltest_synchronous.cc

 // Copyright 2014 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 "build/build_config.h"
 #include "cc/layers/content_layer_client.h"
 #include "cc/layers/picture_image_layer.h"
 #include "cc/layers/picture_layer.h"
 #include "cc/layers/solid_color_layer.h"
 #include "cc/test/fake_content_layer_client.h"
 #include "cc/test/layer_tree_pixel_test.h"
 #include "cc/test/pixel_comparator.h"
 
 #if !defined(OS_ANDROID)
 
 namespace cc {
 namespace {
 
 class LayerTreeHostSynchronousPixelTest : public LayerTreePixelTest {
  public:
   void InitializeSettings(LayerTreeSettings* settings) override {
     LayerTreePixelTest::InitializeSettings(settings);
     settings->single_thread_proxy_scheduler = false;
+    settings->use_zero_copy = true;
   }
 
   void BeginTest() override {
     LayerTreePixelTest::BeginTest();
     PostCompositeImmediatelyToMainThread();
   }
 };
 
 TEST_F(LayerTreeHostSynchronousPixelTest, OneContentLayer) {
   gfx::Size bounds(200, 200);
@@ skipping 37 matching lines @@
   root->SetIsDrawable(true);
 
   RunSingleThreadedPixelTest(PIXEL_TEST_GL, root,
                              base::FilePath(FILE_PATH_LITERAL("green.png")));
 }
 
 }  // namespace
 }  // namespace cc
 
 #endif  // OS_ANDROID