mus: Turn off using BeginFrameSource in ui::Compositor.

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 <stddef.h>
 
 #include <algorithm>
 #include <deque>
@@ skipping 27 matching lines @@
 #include "ui/compositor/layer.h"
 #include "ui/compositor/layer_animator_collection.h"
 #include "ui/gl/gl_context.h"
 #include "ui/gl/gl_switches.h"
 
 namespace {
 
 const double kDefaultRefreshRate = 60.0;
 const double kTestRefreshRate = 200.0;
 
+bool IsRunningInMojoShell(base::CommandLine* command_line) {
+  const char kMojoShellFlag[] = "mojo-platform-channel-handle";
+  return command_line->HasSwitch(kMojoShellFlag);
+}
+
 }  // namespace
 
 namespace ui {
 
 CompositorLock::CompositorLock(Compositor* compositor)
     : compositor_(compositor) {
   if (compositor_->locks_will_time_out_) {
     compositor_->task_runner_->PostDelayedTask(
         FROM_HERE,
         base::Bind(&CompositorLock::CancelLock, AsWeakPtr()),
@@ skipping 110 matching lines @@
     DCHECK_GT(settings.use_image_texture_targets.size(), format);
     settings.use_image_texture_targets[format] =
         context_factory_->GetImageTextureTarget(
             static_cast<gfx::BufferFormat>(format), usage);
   }
 
   // Note: Only enable image decode tasks if we have more than one worker
   // thread.
   settings.image_decode_tasks_enabled = false;
 
-  settings.use_output_surface_begin_frame_source = true;
+  // TODO(crbug.com/603600): This should always be turned on once mus tells its
+  // clients about BeginFrame.
+  settings.use_output_surface_begin_frame_source =
+      !IsRunningInMojoShell(command_line);
 
 #if !defined(OS_ANDROID)
   // TODO(sohanjg): Revisit this memory usage in tile manager.
   cc::ManagedMemoryPolicy policy(
       512 * 1024 * 1024, gpu::MemoryAllocation::CUTOFF_ALLOW_NICE_TO_HAVE,
       settings.memory_policy_.num_resources_limit);
   settings.memory_policy_ = policy;
 #endif
 
   base::TimeTicks before_create = base::TimeTicks::Now();
@@ skipping 339 matching lines @@
                     observer_list_,
                     OnCompositingLockStateChanged(this));
 }
 
 void Compositor::CancelCompositorLock() {
   if (compositor_lock_)
     compositor_lock_->CancelLock();
 }
 
 }  // namespace ui