Reland HTMLPlugInElement: Use custom focus logic only when there is a plugin.

Source/core/html/HTMLPlugInElement.h

Index: Source/core/html/HTMLPlugInElement.h
diff --git a/Source/core/html/HTMLPlugInElement.h b/Source/core/html/HTMLPlugInElement.h
index 3997868c69dc8f38d687b510bbf46e057e68ed54..e7152daa33ae4b033db23e84cdc37eb6d38e7b38 100644
--- a/Source/core/html/HTMLPlugInElement.h
+++ b/Source/core/html/HTMLPlugInElement.h
@@ -52,8 +52,16 @@ public:
 #endif
 
     void resetInstance();
+
+    // Returns the existing plugin widget, if there is one.
+    Widget* existingPluginWidget() const;
+
+    // Returns the plugin widget, forcing layout and post-layout tasks
+    // to happen synchronously (e.g. for JS bindings).
+    // See also renderPartForJSBindings().
+    Widget* pluginWidgetForJSBindings();
+
     SharedPersistent<v8::Object>* pluginWrapper();
-    Widget* pluginWidget() const;
     NPObject* getNPObject();
     bool canProcessDrag() const;
     const String& url() const { return m_url; }