Fixed overlapping subtle notifications on Mac.

chrome/browser/ui/cocoa/browser/exclusive_access_controller_views.mm

 // Copyright 2016 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/browser/exclusive_access_controller_views.h"
 
 #include "chrome/browser/download/download_shelf.h"
 #include "chrome/browser/fullscreen.h"
 #include "chrome/browser/ui/browser_window.h"
 #include "chrome/browser/ui/cocoa/accelerators_cocoa.h"
@@ skipping 18 matching lines @@
   pref_registrar_.Add(
       prefs::kShowFullscreenToolbar,
       base::Bind(&ExclusiveAccessController::UpdateFullscreenToolbar,
                  base::Unretained(this)));
 }
 
 ExclusiveAccessController::~ExclusiveAccessController() {}
 
 void ExclusiveAccessController::Show() {
   if (ExclusiveAccessManager::IsSimplifiedFullscreenUIEnabled()) {
+    // Hide the backspace shortcut bubble, to avoid overlapping.
+    new_back_shortcut_bubble_.reset();
+
     views_bubble_.reset(
         new ExclusiveAccessBubbleViews(this, url_, bubble_type_));
     return;
   }
 
   [cocoa_bubble_ closeImmediately];
   cocoa_bubble_.reset([[ExclusiveAccessBubbleWindowController alloc]
                  initWithOwner:controller_
       exclusive_access_manager:browser_->exclusive_access_manager()
                        profile:browser_->profile()
                            url:url_
                     bubbleType:bubble_type_]);
   [cocoa_bubble_ showWindow];
 }
 
 void ExclusiveAccessController::ShowNewBackShortcutBubble(bool forward) {
+  // Hide the exclusive access bubble, to avoid overlapping.
+  views_bubble_.reset();
+
   if (new_back_shortcut_bubble_)
     new_back_shortcut_bubble_->UpdateContent(forward);
   else
     new_back_shortcut_bubble_.reset(new NewBackShortcutBubble(this, forward));
 }
 
 void ExclusiveAccessController::Destroy() {
   views_bubble_.reset();
   [cocoa_bubble_ closeImmediately];
   cocoa_bubble_.reset();
@@ skipping 126 matching lines @@
 }
 
 gfx::Rect ExclusiveAccessController::GetTopContainerBoundsInScreen() {
   NOTREACHED();  // Only used for ImmersiveMode.
   return gfx::Rect();
 }
 
 BrowserWindow* ExclusiveAccessController::GetBrowserWindow() const {
   return [controller_ browserWindow];
 }