cc: Introduce CompositorMode enum.

cc/test/fake_layer_tree_host.cc

 // Copyright 2013 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/fake_layer_tree_host.h"
 
 #include "cc/layers/layer.h"
 #include "cc/test/test_task_graph_runner.h"
 
 namespace cc {
 FakeLayerTreeHost::FakeLayerTreeHost(FakeLayerTreeHostClient* client,
                                      LayerTreeHost::InitParams* params)
-    : LayerTreeHost(params),
+    : LayerTreeHost(params, CompositorMode::SingleThreaded),
       client_(client),
       host_impl_(*params->settings,
                  &task_runner_provider_,
                  &manager_,
                  params->task_graph_runner),
       needs_commit_(false),
       renderer_capabilities_set(false) {
   client_->SetLayerTreeHost(this);
 }
 
@@ skipping 45 matching lines @@
         page_scale_layer()->id(), inner_viewport_scroll_layer()->id(),
         outer_viewport_scroll_layer() ? outer_viewport_scroll_layer()->id()
                                       : Layer::INVALID_ID);
   }
 
   active_tree()->UpdatePropertyTreesForBoundsDelta();
   return active_tree()->root_layer();
 }
 
 }  // namespace cc