mus: Make --use-mus-in-renderer the default for --mash.

content/browser/renderer_host/render_widget_host_view_aura.cc

 // 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.
 
 #include "content/browser/renderer_host/render_widget_host_view_aura.h"
 
 #include <set>
 #include <utility>
 
 #include "base/auto_reset.h"
@@ skipping 350 matching lines @@
   }
 
   RenderWidgetHostViewAura* view_;
   std::set<aura::Window*> ancestors_;
 
   DISALLOW_COPY_AND_ASSIGN(WindowAncestorObserver);
 };
 
 bool IsMus() {
   return aura::Env::GetInstance()->mode() == aura::Env::Mode::MUS &&
-         base::CommandLine::ForCurrentProcess()->HasSwitch(
-             switches::kUseMusInRenderer);
+         !base::CommandLine::ForCurrentProcess()->HasSwitch(
+             switches::kNoUseMusInRenderer);
 }
 
 ////////////////////////////////////////////////////////////////////////////////
 // RenderWidgetHostViewAura, public:
 
 RenderWidgetHostViewAura::RenderWidgetHostViewAura(RenderWidgetHost* host,
                                                    bool is_guest_view_hack)
     : host_(RenderWidgetHostImpl::From(host)),
       window_(nullptr),
       in_shutdown_(false),
@@ skipping 2004 matching lines @@
 
 void RenderWidgetHostViewAura::SetPopupChild(
     RenderWidgetHostViewAura* popup_child_host_view) {
   popup_child_host_view_ = popup_child_host_view;
   event_handler_->SetPopupChild(
       popup_child_host_view,
       popup_child_host_view ? popup_child_host_view->event_handler() : nullptr);
 }
 
 }  // namespace content