Prevent sending click event for non primary button

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

Index: third_party/WebKit/Source/core/input/EventHandler.cpp
diff --git a/third_party/WebKit/Source/core/input/EventHandler.cpp b/third_party/WebKit/Source/core/input/EventHandler.cpp
index 4a88d4598398c243cde77a02e86ba1b3fd74ad95..f08c6abd29ad6d2d2b076335914bd6fc509c9310 100644
--- a/third_party/WebKit/Source/core/input/EventHandler.cpp
+++ b/third_party/WebKit/Source/core/input/EventHandler.cpp
@@ -1487,13 +1487,23 @@ WebInputEventResult EventHandler::handleMouseReleaseEvent(const PlatformMouseEve
         m_clickNode->updateDistribution();
         if (Node* clickTargetNode = mev.innerNode()->commonAncestor(
             *m_clickNode, parentForClickEvent)) {
-
             // 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));
         }
     }