Enable the simplified-fullscreen-ui flag by default on Aura.

chrome/browser/ui/exclusive_access/exclusive_access_manager.cc

 // Copyright (c) 2015 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.
 
 #include "chrome/browser/ui/exclusive_access/exclusive_access_manager.h"
 
 #include "base/command_line.h"
 #include "build/build_config.h"
 #include "chrome/browser/app_mode/app_mode_utils.h"
 #include "chrome/browser/ui/browser.h"
@@ skipping 83 matching lines @@
   if (base::CommandLine::ForCurrentProcess()->HasSwitch(
           switches::kEnableSimplifiedFullscreenUI)) {
     return true;
   }
 
   if (base::CommandLine::ForCurrentProcess()->HasSwitch(
           switches::kDisableSimplifiedFullscreenUI)) {
     return false;
   }
 
+  // Enabled by default on Aura platforms only.
+#if defined(USE_AURA)
+  return true;
+#else
   return false;
+#endif  // defined(USE_AURA)
 }
 
 void ExclusiveAccessManager::OnTabDeactivated(WebContents* web_contents) {
   fullscreen_controller_.OnTabDeactivated(web_contents);
   mouse_lock_controller_.OnTabDeactivated(web_contents);
 }
 
 void ExclusiveAccessManager::OnTabDetachedFromView(WebContents* web_contents) {
   fullscreen_controller_.OnTabDetachedFromView(web_contents);
   mouse_lock_controller_.OnTabDetachedFromView(web_contents);
@@ skipping 29 matching lines @@
   bool updateBubble = mouse_lock_controller_.OnDenyExclusiveAccessPermission();
   updateBubble |= fullscreen_controller_.OnDenyExclusiveAccessPermission();
   if (updateBubble)
     UpdateExclusiveAccessExitBubbleContent();
 }
 
 void ExclusiveAccessManager::ExitExclusiveAccess() {
   fullscreen_controller_.ExitExclusiveAccessToPreviousState();
   mouse_lock_controller_.LostMouseLock();
 }