Remove the --ui-enable-threaded-compositing flag.

ui/compositor/compositor_switches.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_switches.h"
 
 #include "base/command_line.h"
 
 namespace switches {
 
 const char kDisableTestCompositor[] = "disable-test-compositor";
 
 const char kUIDisableDeadlineScheduling[] = "ui-disable-deadline-scheduling";
 
 const char kUIDisableThreadedCompositing[] = "ui-disable-threaded-compositing";
 
 const char kUIEnableDeadlineScheduling[] = "ui-enable-deadline-scheduling";
 
 const char kUIEnableSoftwareCompositing[] = "ui-enable-software-compositing";
 
-const char kUIEnableThreadedCompositing[] = "ui-enable-threaded-compositing";
-
 const char kUIMaxFramesPending[] = "ui-max-frames-pending";
 
 const char kUIShowPaintRects[] = "ui-show-paint-rects";
 
 bool IsUIDeadlineSchedulingEnabled() {
   const CommandLine& command_line = *CommandLine::ForCurrentProcess();
 
   // Default to disabled.
   bool enabled = false;
 
   // Default to enabled for Aura.
   enabled = true;
 
   // Flags override.
   enabled |= command_line.HasSwitch(switches::kUIEnableDeadlineScheduling);
   enabled &= !command_line.HasSwitch(switches::kUIDisableDeadlineScheduling);
 
   return enabled;
 }
 
 }  // namespace switches