Fix OSX 10.12 compilation errors in chrome/browser/ui.

chrome/browser/ui/cocoa/sprite_view.mm

 // 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.
 
 #import "chrome/browser/ui/cocoa/sprite_view.h"
 
 #import <QuartzCore/CAAnimation.h>
 #import <QuartzCore/CATransaction.h>
 
 #include "base/logging.h"
+#import "base/mac/sdk_forward_declarations.h"
 #include "ui/base/cocoa/animation_utils.h"
 
 static const CGFloat kFrameDuration = 0.03;  // 30ms for each animation frame.
 
+@interface SpriteView (Private) <CALayerDelegate>
+@end
+
 @implementation SpriteView
 
 - (instancetype)initWithFrame:(NSRect)frame {
   if (self = [super initWithFrame:frame]) {
     // A layer-hosting view. It will clip its sublayers,
     // if they exceed the boundary.
     CALayer* layer = [CALayer layer];
     layer.masksToBounds = YES;
 
     imageLayer_ = [CALayer layer];
@@ skipping 138 matching lines @@
   }
 }
 
 - (BOOL)layer:(CALayer*)layer
     shouldInheritContentsScale:(CGFloat)scale
                     fromWindow:(NSWindow*)window {
   return YES;
 }
 
 @end