Make --disable-gpu-vsync work with CoreAnimation

content/browser/renderer_host/compositing_iosurface_layer_mac.mm

 // 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 "content/browser/renderer_host/compositing_iosurface_layer_mac.h"
 
 #include <CoreFoundation/CoreFoundation.h>
 #include <OpenGL/gl.h>
 
 #include "base/mac/sdk_forward_declarations.h"
@@ skipping 39 matching lines @@
   return self;
 }
 
 - (void)disableCompositing{
   ScopedCAActionDisabler disabler;
   [self removeFromSuperlayer];
   renderWidgetHostView_ = nil;
 }
 
 - (void)gotNewFrame {
-  if (![self isAsynchronous]) {
-    [self setNeedsDisplay];
-    [self setAsynchronous:YES];
+  if ([self isAsynchronous]) {
+    needsDisplay_ = YES;
   } else {
-    needsDisplay_ = YES;
+    // Calls to setNeedsDisplay can sometimes be ignored, especially if issued
+    // rapidly (e.g, with vsync off). This is unacceptable because the failure
+    // to ack a single frame will hang the renderer. Call setNeedsDisplay and
+    // displayIfNeeded in a loop to ensure the call goes through.
+    do {
+      [self setNeedsDisplay];
+      [self displayIfNeeded];
+    } while (needsDisplay_);
+
+    // If vsync is disabled, don't bother trying to use the isAsynchronous
+    // property to ensure smooth animation.
+    if (!context_ || !context_->is_vsync_disabled()) {
+      [self setAsynchronous:YES];
+    }
   }
 }
 
 - (void)timerSinceGotNewFrameFired {
   if (![self isAsynchronous])
     return;
 
   [self setAsynchronous:NO];
-  if (needsDisplay_)
+
+  // If there was a pending frame, ensure that it goes through.
+  while (needsDisplay_) {
     [self setNeedsDisplay];
+    [self displayIfNeeded];
+  }
 }
 
 - (void)waitForResizedFrameInContext:(CGLContextObj)glContext {
   // Cache a copy of renderWidgetHostView_ because it may be reset if
   // a software frame is received in GetBackingStore.
   content::RenderWidgetHostViewMac* cached_view = renderWidgetHostView_;
   if (!cached_view->render_widget_host_ ||
       cached_view->render_widget_host_->is_hidden()) {
     return;
   }
@@ skipping 86 matching lines @@
         context_,
         window_rect,
         window_scale_factor,
         false)) {
     renderWidgetHostView_->GotAcceleratedCompositingError();
     return;
   }
 
   needsDisplay_ = NO;
   renderWidgetHostView_->SendPendingLatencyInfoToHost();
+

[ccameron, 2014/02/20 10:42:59]

This is to match the behavior of WebKit. The claim is that the super method will
trigger a required flush (I have not observed a change in behavior).

+  [super drawInCGLContext:glContext
+              pixelFormat:pixelFormat
+             forLayerTime:timeInterval
+              displayTime:timeStamp];
 }
 
 @end