Add supportsInputMethod() interface for WebPlugin.

Source/core/html/HTMLPlugInElement.cpp

 /**
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2000 Stefan Schimanski (1Stein@gmx.de)
  * Copyright (C) 2004, 2005, 2006 Apple Computer, Inc.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
@@ skipping 507 matching lines @@
 {
     if (root.isOldestAuthorShadowRoot())
         lazyReattachIfAttached();
 }
 
 bool HTMLPlugInElement::useFallbackContent() const
 {
     return hasAuthorShadowRoot();
 }
 
+bool HTMLPlugInElement::canHandleInputMethod() const
+{
+    if (!document().page())
+        return false;
+    return pluginWidget() && pluginWidget()->isPluginView() && toPluginView(pluginWidget())->supportsInputMethod();
 }
+
+}