Update IOSurface scale factor before compare

content/browser/renderer_host/render_widget_host_view_mac.mm

 // 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 "content/browser/renderer_host/render_widget_host_view_mac.h"
 
 #include <QuartzCore/QuartzCore.h>
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
@@ skipping 1310 matching lines @@
   if (compositing_iosurface_)
     compositing_iosurface_->UnrefIOSurface();
 }
 
 void RenderWidgetHostViewMac::AcceleratedSurfaceRelease() {
   compositing_iosurface_.reset();
 }
 
 bool RenderWidgetHostViewMac::HasAcceleratedSurface(
       const gfx::Size& desired_size) {
+  // Update device scale factor for the IOSurface before checking if there
+  // is a match. When initially created, the IOSurface is unaware of its
+  // scale factor, which can result in compatible IOSurfaces not being used
+  // http://crbug.com/237293
+  if (compositing_iosurface_.get() &&
+      compositing_iosurface_->HasIOSurface()) {
+    compositing_iosurface_->SetDeviceScaleFactor(ScaleFactor(cocoa_view_));

[Ken Russell (switch to Gerrit), 2013/05/07 19:23:51]

It seems odd that this is done as a side-effect of calling
HasAcceleratedSurface. Is there a more obvious place this could be done?

[ccameron, 2013/05/07 19:27:36]

Yes, this I was unhappy with this too. The other place this happens is in Draw
(which also doesn't make too much sense to have side effects on resolution).

The version that I'm working on for trunk has no side effects here (but has lots
more diffs).

+  }
+
   return last_frame_was_accelerated_ &&
          compositing_iosurface_.get() &&
          compositing_iosurface_->HasIOSurface() &&
          (desired_size.IsEmpty() ||
           compositing_iosurface_->io_surface_size() == desired_size);
 }
 
 void RenderWidgetHostViewMac::AboutToWaitForBackingStoreMsg() {
   AckPendingSwapBuffers();
 }
@@ skipping 2029 matching lines @@
   if (!string) return NO;
 
   // If the user is currently using an IME, confirm the IME input,
   // and then insert the text from the service, the same as TextEdit and Safari.
   [self confirmComposition];
   [self insertText:string];
   return YES;
 }
 
 @end