Add supportsInputMethod() interface for WebPlugin.

Source/web/WebViewImpl.h

Index: Source/web/WebViewImpl.h
diff --git a/Source/web/WebViewImpl.h b/Source/web/WebViewImpl.h
index 5df4efa70e9bfd256cd23bec275059e983dc0867..6680ff4786c30821430a56993603d123f5a1fe90 100644
--- a/Source/web/WebViewImpl.h
+++ b/Source/web/WebViewImpl.h
@@ -109,6 +109,7 @@ class WebLayerTreeView;
 class WebMouseEvent;
 class WebMouseWheelEvent;
 class WebPagePopupImpl;
+class WebPlugin;
 class WebPrerendererClient;
 class WebSettingsImpl;
 class WebTouchEvent;
@@ -643,6 +644,7 @@ private:
     void closePendingHelperPlugins(WebCore::Timer<WebViewImpl>*);
 
     WebCore::InputMethodContext* inputMethodContext();
+    WebPlugin* focusedPluginIfInputMethodSupported(WebCore::Frame*);
 
     WebViewClient* m_client; // Can be 0 (e.g. unittests, shared workers, etc.)
     WebAutofillClient* m_autofillClient;