Prevent sending click event for non primary button

third_party/WebKit/Source/core/input/EventHandler.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2006 Alexey Proskuryakov (ap@webkit.org)
  * Copyright (C) 2012 Digia Plc. and/or its subsidiary(-ies)
  *
  * 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.
@@ skipping 1512 matching lines @@
             m_clickNode->updateDistribution();
             mev.innerNode()->updateDistribution();
             clickTargetNode = mev.innerNode()->commonAncestor(
                 *m_clickNode, parentForClickEvent);
         }
         if (clickTargetNode) {
             // Dispatch mouseup directly w/o calling updateMouseEventTargetNodeAndSendEvents
             // because the mouseup dispatch above has already updated it
             // correctly. Moreover, clickTargetNode is different from
             // mev.innerNode at drag-release.
-            clickEventResult = toWebInputEventResult(clickTargetNode->dispatchMouseEvent(mev.event(),
-                EventTypeNames::click, m_clickCount));
+
+            MouseEvent* event = MouseEvent::create(
+                EventTypeNames::click,
+                clickTargetNode->document().domWindow(),
+                mev.event(), m_clickCount, nullptr);
+
+            // This is to suppress sending click events for non-primary buttons.
+            // But still doing default action like opening a new tab for middle
+            // click (crbug.com/255).
+            if (mev.event().button() != MouseButton::LeftButton)
+                event->stopPropagation();
+
+            clickEventResult = toWebInputEventResult(clickTargetNode->dispatchEvent(event));
         }
     }
 
     if (m_resizeScrollableArea) {
         m_resizeScrollableArea->setInResizeMode(false);
         m_resizeScrollableArea = nullptr;
     }
 
     if (eventResult == WebInputEventResult::NotHandled)
         eventResult = handleMouseReleaseEvent(mev);
@@ skipping 2630 matching lines @@
 PlatformEvent::Modifiers EventHandler::accessKeyModifiers()
 {
 #if OS(MACOSX)
     return static_cast<PlatformEvent::Modifiers>(PlatformEvent::CtrlKey | PlatformEvent::AltKey);
 #else
     return PlatformEvent::AltKey;
 #endif
 }
 
 } // namespace blink