Animations: Implement runtime flag for enabling compositor animation timelines.

ui/compositor/compositor.cc

 // Copyright (c) 2012 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 "ui/compositor/compositor.h"
 
 #include <algorithm>
 #include <deque>
 
 #include "base/bind.h"
@@ skipping 120 matching lines @@
       command_line->HasSwitch(cc::switches::kEnableGpuBenchmarking));
 
   settings.impl_side_painting = IsUIImplSidePaintingEnabled();
   settings.use_zero_copy = IsUIZeroCopyEnabled();
   settings.use_one_copy = IsUIOneCopyEnabled();
   settings.use_image_texture_target = context_factory_->GetImageTextureTarget();
   // Note: gathering of pixel refs is only needed when using multiple
   // raster threads.
   settings.gather_pixel_refs = false;
 
+  settings.use_compositor_animation_timelines =
+      command_line->HasSwitch(switches::kUIEnableCompositorAnimationTimelines);
+
   base::TimeTicks before_create = base::TimeTicks::Now();
   host_ = cc::LayerTreeHost::CreateSingleThreaded(
       this, this, context_factory_->GetSharedBitmapManager(),
       context_factory_->GetGpuMemoryBufferManager(),
       context_factory_->GetTaskGraphRunner(), settings, task_runner_, nullptr);
   UMA_HISTOGRAM_TIMES("GPU.CreateBrowserCompositor",
                       base::TimeTicks::Now() - before_create);
   host_->SetRootLayer(root_web_layer_);
   host_->set_surface_id_namespace(surface_id_allocator_->id_namespace());
   host_->SetLayerTreeHostClientReady();
@@ skipping 266 matching lines @@
                     observer_list_,
                     OnCompositingLockStateChanged(this));
 }
 
 void Compositor::CancelCompositorLock() {
   if (compositor_lock_)
     compositor_lock_->CancelLock();
 }
 
 }  // namespace ui