Make cross-process CALayers work on Mac

ui/base/cocoa/remote_layer_api.h

+// Copyright 2014 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.
+
+#ifndef UI_BASE_COCOA_REMOTE_LAYER_API_H_
+#define UI_BASE_COCOA_REMOTE_LAYER_API_H_
+
+#if defined(__OBJC__)
+#import <Cocoa/Cocoa.h>
+#endif  // __OBJC__
+
+#include "ui/base/ui_base_export.h"
+
+// The CGSConnectionID is used to create the CAContext in the process that is
+// going to share the CALayers that it is rendering to another process to
+// display.
+extern "C" {
+typedef uint32_t CGSConnectionID;
+CGSConnectionID CGSMainConnectionID(void);

[Avi (use Gerrit), 2014/06/20 00:15:11]

I'm a bit surprised we don't already have definitions for this already
somewhere...

[ccameron, 2014/06/20 00:55:06]

The definition seems pretty obscure -- a search on site:apple.com only gets 3
hits (none of them documentation).

+};
+
+// The CAContextID type identifies a CAContext across processes. This is the
+// token that is passed from the process that is sharing the CALayer that it is
+// rendering to the process that will be displaying that CALayer.
+typedef uint32_t CAContextID;
+
+#if defined(__OBJC__)
+
+// The CAContext has a static CAContextID which can be sent to another process.
+// When a CALayerHost is created using that CAContextID in another process, the
+// content displayed by that CALayerHost will be the content of the CALayer
+// that is set as the |layer| property on the CAContext.
+@interface CAContext : NSObject
+{
+}

[Avi (use Gerrit), 2014/06/20 00:15:11]

Pretty sure you can omit the braces here...

[ccameron, 2014/06/20 00:55:06]

Done.

++ (id)contextWithCGSConnection:(CAContextID)contextId options:(NSDictionary*)optionsDict;

[Avi (use Gerrit), 2014/06/20 00:15:11]

80 cols

[ccameron, 2014/06/20 00:55:06]

How did this pass presubmit?? Done.

+@property(readonly) CAContextID contextId;
+@property(retain) CALayer *layer;
+@end
+
+// The CALayerHost is created in the process that will display the content
+// being rendered by another process. Setting the |contextId| property on
+// an object of this class will make this layer display the content of the
+// CALayer that is set to the CAContext with that CAContextID in the layer
+// sharing process.
+@interface CALayerHost : CALayer
+{
+}

[Avi (use Gerrit), 2014/06/20 00:15:11]

...and the braces here.

[ccameron, 2014/06/20 00:55:06]

Done.

+@property CAContextID contextId;
+@end
+
+#endif // __OBJC__
+
+namespace ui {
+
+// This function will check if all of the interfaces listed above are supported
+// on the system, and return true if they are.
+bool UI_BASE_EXPORT RemoteLayerAPISupported();
+
+}  // namespace ui
+
+#endif  // UI_BASE_COCOA_REMOTE_LAYER_API_H_