mac: Fix a history swiper bug where the shield wouldn't disappear.

chrome/browser/ui/cocoa/history_overlay_controller.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.
 
 #import "chrome/browser/ui/cocoa/history_overlay_controller.h"
 
 #include "base/logging.h"
 #import "chrome/browser/ui/cocoa/browser_window_controller.h"
 #include "grit/theme_resources.h"
 #include "ui/base/resource/resource_bundle.h"
@@ skipping 71 matching lines @@
 
 - (id)initForMode:(HistoryOverlayMode)mode {
   if ((self = [super init])) {
     mode_ = mode;
     DCHECK(mode == kHistoryOverlayModeBack ||
            mode == kHistoryOverlayModeForward);
   }
   return self;
 }
 
-- (void)dealloc {
-  [[BrowserWindowController
-      browserWindowControllerForView:[self view]] onOverlappedViewHidden];
-  [self.view removeFromSuperview];
-  [super dealloc];
-}
-
 - (void)loadView {
   const gfx::Image& image =
       ui::ResourceBundle::GetSharedInstance().GetNativeImageNamed(
           mode_ == kHistoryOverlayModeBack ? IDR_SWIPE_BACK
                                            : IDR_SWIPE_FORWARD);
   contentView_.reset(
       [[HistoryOverlayView alloc] initWithMode:mode_
                                          image:image.ToNSImage()]);
   self.view = contentView_;
 }
@@ skipping 36 matching lines @@
   [[parent_ superview] addSubview:self.view
                        positioned:NSWindowAbove
                        relativeTo:parent_];
   [[BrowserWindowController
       browserWindowControllerForView:[self view]] onOverlappedViewShown];
 }
 
 - (void)dismiss {
   const CGFloat kFadeOutDurationSeconds = 0.4;
 
+  [NSAnimationContext beginGrouping];
+  [NSAnimationContext currentContext].duration = kFadeOutDurationSeconds;
   NSView* overlay = self.view;
 
   base::scoped_nsobject<CAAnimation> animation(
       [[overlay animationForKey:@"alphaValue"] copy]);
   [animation setDelegate:self];
   [animation setDuration:kFadeOutDurationSeconds];
   NSMutableDictionary* dictionary =
       [NSMutableDictionary dictionaryWithCapacity:1];
   [dictionary setObject:animation forKey:@"alphaValue"];
   [overlay setAnimations:dictionary];
   [[overlay animator] setAlphaValue:0.0];
+  [NSAnimationContext endGrouping];
 }
 
 - (void)animationDidStop:(CAAnimation*)theAnimation finished:(BOOL)finished {
+  [[BrowserWindowController
+      browserWindowControllerForView:[self view]] onOverlappedViewHidden];
+  [self.view removeFromSuperview];
   // Destroy the CAAnimation and its strong reference to its delegate (this
   // class).
   [self.view setAnimations:nil];
 }
 
 @end