Add vsync notification command line switch

cc/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 "cc/switches.h"
 
 namespace cc {
 namespace switches {
 
 // On platforms where checkerboards are used, prefer background colors instead
@@ skipping 53 matching lines @@
 const char kTraceOverdraw[] = "trace-overdraw";
 
 // Re-rasters everything multiple times to simulate a much slower machine.
 // Give a scale factor to cause raster to take that many times longer to
 // complete, such as --slow-down-raster-scale-factor=25.
 const char kSlowDownRasterScaleFactor[] = "slow-down-raster-scale-factor";
 
 // Schedule rasterization jobs according to their estimated processing cost.
 const char kUseCheapnessEstimator[] = "use-cheapness-estimator";
 
+// Use a vsync signal from the browser to the renderer to schedule rendering.
+const char kEnableVsyncNotification[] = "enable-vsync-notification";
+
 }  // namespace switches
 }  // namespace cc