Have Node::document() return a reference instead of a pointer

Source/web/EditorClientImpl.cpp

 /*
  * Copyright (C) 2006, 2007 Apple, Inc.  All rights reserved.
  * Copyright (C) 2012 Google, Inc.  All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 522 matching lines @@
     return mapKey ? keyPressCommandsMap->get(mapKey) : 0;
 }
 
 bool EditorClientImpl::handleEditingKeyboardEvent(KeyboardEvent* evt)
 {
     const PlatformKeyboardEvent* keyEvent = evt->keyEvent();
     // do not treat this as text input if it's a system key event
     if (!keyEvent || keyEvent->isSystemKey())
         return false;
 
-    Frame* frame = evt->target()->toNode()->document()->frame();
+    Frame* frame = evt->target()->toNode()->document().frame();
     if (!frame)
         return false;
 
     String commandName = interpretKeyEvent(evt);
     Editor::Command command = frame->editor().command(commandName);
 
     if (keyEvent->type() == PlatformEvent::RawKeyDown) {
         // WebKit doesn't have enough information about mode to decide how
         // commands that just insert text if executed via Editor should be treated,
         // so we leave it upon WebCore to either handle them immediately
@@ skipping 222 matching lines @@
 #endif
 }
 
 void EditorClientImpl::willSetInputMethodState()
 {
     if (m_webView->client())
         m_webView->client()->resetInputMethod();
 }
 
 } // namesace WebKit