Make --disable-gpu-vsync work with CoreAnimation

content/browser/renderer_host/compositing_iosurface_layer_mac.mm

Index: content/browser/renderer_host/compositing_iosurface_layer_mac.mm
diff --git a/content/browser/renderer_host/compositing_iosurface_layer_mac.mm b/content/browser/renderer_host/compositing_iosurface_layer_mac.mm
index 2f2068e036206867b0871d5cadec9b016ecd0121..212fd67a85dedabaa9bf2e475c927e4ae9eab1f4 100644
--- a/content/browser/renderer_host/compositing_iosurface_layer_mac.mm
+++ b/content/browser/renderer_host/compositing_iosurface_layer_mac.mm
@@ -57,11 +57,23 @@
 }
 
 - (void)gotNewFrame {
-  if (![self isAsynchronous]) {
-    [self setNeedsDisplay];
-    [self setAsynchronous:YES];
-  } else {
+  if ([self isAsynchronous]) {
     needsDisplay_ = YES;
+  } else {
+    // 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];
+    }
   }
 }
 
@@ -70,8 +82,12 @@
     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 {
@@ -178,6 +194,11 @@
 
   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