Prevent crash in NativeWidgetAura::IsMouseEventsEnabled() when no root window

ui/views/widget/native_widget_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 "ui/views/widget/native_widget_aura.h"
 
 #include "base/bind.h"
 #include "base/location.h"
 #include "base/memory/ptr_util.h"
 #include "base/single_thread_task_runner.h"
@@ skipping 647 matching lines @@
 
 void NativeWidgetAura::SetCursor(gfx::NativeCursor cursor) {
   cursor_ = cursor;
   aura::client::CursorClient* cursor_client =
       aura::client::GetCursorClient(window_->GetRootWindow());
   if (cursor_client)
     cursor_client->SetCursor(cursor);
 }
 
 bool NativeWidgetAura::IsMouseEventsEnabled() const {
-  if (!window_)
+  if (!window_ || !window_->GetRootWindow())
     return false;
   aura::client::CursorClient* cursor_client =
       aura::client::GetCursorClient(window_->GetRootWindow());
   return cursor_client ? cursor_client->IsMouseEventsEnabled() : true;
 }
 
 void NativeWidgetAura::ClearNativeFocus() {
   aura::client::FocusClient* client = aura::client::GetFocusClient(window_);
   if (window_ && client && window_->Contains(client->GetFocusedWindow()))
     client->ResetFocusWithinActiveWindow(window_);
@@ skipping 510 matching lines @@
     gfx::NativeView native_view) {
   aura::client::CaptureClient* capture_client =
       aura::client::GetCaptureClient(native_view->GetRootWindow());
   if (!capture_client)
     return nullptr;
   return capture_client->GetGlobalCaptureWindow();
 }
 
 }  // namespace internal
 }  // namespace views