Make plugin elements return false from canStartSelection.

third_party/WebKit/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 84 matching lines @@
         }
     }
     m_persistedPluginWidget = widget;
 }
 
 bool HTMLPlugInElement::canProcessDrag() const
 {
     return pluginWidget() && pluginWidget()->isPluginView() && toPluginView(pluginWidget())->canProcessDrag();
 }
 
+bool HTMLPlugInElement::canStartSelection() const
+{
+    if (!useFallbackContent())

[yosin_UTC9, 2016/06/22 01:23:18]

How about below?

return useFallbackContent() && Node::canStartSelection();

[aelias_OOO_until_Jul13, 2016/06/22 01:33:03]

Done.

+        return false;
+
+    return Node::canStartSelection();
+}
+
 bool HTMLPlugInElement::willRespondToMouseClickEvents()
 {
     if (isDisabledFormControl())
         return false;
     LayoutObject* r = layoutObject();
     return r && (r->isEmbeddedObject() || r->isLayoutPart());
 }
 
 void HTMLPlugInElement::removeAllEventListeners()
 {
@@ skipping 483 matching lines @@
 
 void HTMLPlugInElement::lazyReattachIfNeeded()
 {
     if (!useFallbackContent() && needsWidgetUpdate() && layoutObject() && !isImageType()) {
         lazyReattachIfAttached();
         setPersistedPluginWidget(nullptr);
     }
 }
 
 } // namespace blink