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

chrome/browser/ui/cocoa/confirm_quit_panel_controller.mm

Index: chrome/browser/ui/cocoa/confirm_quit_panel_controller.mm
diff --git a/chrome/browser/ui/cocoa/confirm_quit_panel_controller.mm b/chrome/browser/ui/cocoa/confirm_quit_panel_controller.mm
index 8847281f454f8f665a8d6f46034800543cf01ce7..95eab61d4055574bc724a0ea14c9d4529f4050a9 100644
--- a/chrome/browser/ui/cocoa/confirm_quit_panel_controller.mm
+++ b/chrome/browser/ui/cocoa/confirm_quit_panel_controller.mm
@@ -9,6 +9,7 @@
 
 #include "base/logging.h"
 #include "base/mac/scoped_nsobject.h"
+#import "base/mac/sdk_forward_declarations.h"
 #include "base/metrics/histogram.h"
 #include "base/strings/sys_string_conversions.h"
 #include "chrome/browser/browser_process.h"
@@ -169,7 +170,7 @@ void RegisterLocalState(PrefRegistrySimple* registry) {
 
 // Private Interface ///////////////////////////////////////////////////////////
 
-@interface ConfirmQuitPanelController (Private)
+@interface ConfirmQuitPanelController (Private) <CAAnimationDelegate>
 - (void)animateFadeOut;
 - (NSEvent*)pumpEventQueueForKeyUp:(NSApplication*)app untilDate:(NSDate*)date;
 - (void)hideAllWindowsForApplication:(NSApplication*)app
@@ -355,6 +356,10 @@ ConfirmQuitPanelController* g_confirmQuitPanelController = nil;
   [[window animator] setAlphaValue:0.0];
 }
 
+- (void)animationDidStart:(CAAnimation*)theAnimation {
+  // CAAnimationDelegate method added on OSX 10.12.
+}
+
 - (void)animationDidStop:(CAAnimation*)theAnimation finished:(BOOL)finished {
   [self close];
 }