Support headless content_shell for linux/aura.

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 "base/basictypes.h"
 #include "base/bind.h"
 #include "base/callback_helpers.h"
 #include "base/command_line.h"
@@ skipping 495 matching lines @@
     // to never get a chance to filter events. See crbug.com/160589.
     DCHECK(old_child->popup_parent_host_view_ == popup_parent_host_view_);
     old_child->popup_parent_host_view_ = NULL;
   }
   popup_parent_host_view_->popup_child_host_view_ = this;
   window_->SetType(aura::client::WINDOW_TYPE_MENU);
   window_->Init(ui::LAYER_TEXTURED);
   window_->SetName("RenderWidgetHostViewAura");
 
   aura::Window* root = popup_parent_host_view_->window_->GetRootWindow();
-  aura::client::ParentWindowWithContext(window_, root, bounds_in_screen);
+  if (root)
+    aura::client::ParentWindowWithContext(window_, root, bounds_in_screen);
 
   SetBounds(bounds_in_screen);
   Show();
 }
 
 void RenderWidgetHostViewAura::InitAsFullscreen(
     RenderWidgetHostView* reference_host_view) {
   is_fullscreen_ = true;
   window_->SetType(aura::client::WINDOW_TYPE_NORMAL);
   window_->Init(ui::LAYER_TEXTURED);
@@ skipping 2807 matching lines @@
     RenderWidgetHost* widget) {
   return new RenderWidgetHostViewAura(widget);
 }
 
 // static
 void RenderWidgetHostViewPort::GetDefaultScreenInfo(WebScreenInfo* results) {
   GetScreenInfoForWindow(results, NULL);
 }
 
 }  // namespace content