Mac ÜC: Fix white page hangs

content/browser/compositor/browser_compositor_view_private_mac.mm

Index: content/browser/compositor/browser_compositor_view_private_mac.mm
diff --git a/content/browser/compositor/browser_compositor_view_private_mac.mm b/content/browser/compositor/browser_compositor_view_private_mac.mm
index fb452fb4c9423ac6822cc3bf633598efb3fec00f..c70e5b49a756a0bbbb979d1e7495b1c7eecba657 100644
--- a/content/browser/compositor/browser_compositor_view_private_mac.mm
+++ b/content/browser/compositor/browser_compositor_view_private_mac.mm
@@ -13,6 +13,10 @@
 #include "ui/base/cocoa/animation_utils.h"
 #include "ui/gl/scoped_cgl.h"
 
+@interface CompositingIOSurfaceLayer(Private)
+- (void)immediatelyForceDisplayAndAck;
+@end
+
 ////////////////////////////////////////////////////////////////////////////////
 // BrowserCompositorViewCocoa
 
@@ -98,6 +102,13 @@
   accelerated_latency_info_.insert(accelerated_latency_info_.end(),
                                    latency_info.begin(), latency_info.end());
 
+  // If the client that wanted to display this frame has disappeared, don't
+  // bother creating the layers, just un-block the compositor and quit.
+  if (!client_) {
+    [self layerDidDrawFrame];
+    return;
+  }
+
   // Disable the fade-in animation as the layer is added, removed, or resized.
   ScopedCAActionDisabler disabler;
 
@@ -136,17 +147,16 @@
   // Set the bounds of the accelerated layer to match the size of the frame.
   // If the bounds changed, force the content to be displayed immediately.
   CGRect new_layer_bounds = CGRectMake(
-    0,
-    0,
-    [accelerated_layer_ iosurface]->dip_io_surface_size().width(),
-    [accelerated_layer_ iosurface]->dip_io_surface_size().height());
+      0,
+      0,
+      [accelerated_layer_ iosurface]->dip_io_surface_size().width(),
+      [accelerated_layer_ iosurface]->dip_io_surface_size().height());
   bool bounds_changed = !CGRectEqualToRect(
       new_layer_bounds, [accelerated_layer_ bounds]);
   [accelerated_layer_ setBounds:new_layer_bounds];
   if (bounds_changed ||
       (client_ && client_->BrowserCompositorShouldDrawImmediately())) {
-    [accelerated_layer_ setNeedsDisplay];
-    [accelerated_layer_ displayIfNeeded];
+    [accelerated_layer_ immediatelyForceDisplayAndAck];
   }
 
   // If there was a software layer or an old accelerated layer, remove it.
@@ -166,6 +176,11 @@
   if (!frame_data || !canvas)
     return;
 
+  // If the client that requested frame has disappeared, quit immediately (no
+  // acknowledgement is needed to un-block the software compositor).
+  if (!client_)
+    return;
+
   // If there is not a layer for software frames, create one.
   if (!software_layer_) {
     // Disable the fade-in animation as the layer is added.