Suppress mouseup/down when button is NoButton

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 1357 matching lines @@
     if (m_clickCount > 0 && !contextMenuEvent && mev.innerNode() && m_clickNode && mev.innerNode()->canParticipateInFlatTree() && m_clickNode->canParticipateInFlatTree()) {
         // Updates distribution because a 'mouseup' event listener can make the
         // tree dirty at dispatchMouseEvent() invocation above.
         // Unless distribution is updated, commonAncestor would hit ASSERT.
         // Both m_clickNode and mev.innerNode() don't need to be updated
         // because commonAncestor() will exit early if their documents are different.
         m_clickNode->updateDistribution();
         if (Node* clickTargetNode = mev.innerNode()->commonAncestor(
             *m_clickNode, parentForClickEvent)) {
 
-            // Dispatch mouseup directly w/o calling updateMouseEventTargetNode
-            // 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));
+            // For 4th/5th button in the mouse since Chrome does not yet send
+            // button value to Blink but in some cases it does send the event.
+            // This check is needed to suppress such an event (crbug.com/574959)
+            if (mouseEvent.button() == NoButton) {
+                clickEventResult = WebInputEventResult::HandledSystem;
+            } else {
+                // Dispatch mouseup directly w/o calling updateMouseEventTargetNode
+                // 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));
+            }
         }
     }
 
     if (m_resizeScrollableArea) {
         m_resizeScrollableArea->setInResizeMode(false);
         m_resizeScrollableArea = nullptr;
     }
 
     if (eventResult == WebInputEventResult::NotHandled)
         eventResult = handleMouseReleaseEvent(mev);
@@ skipping 279 matching lines @@
     m_pointerEventManager.elementRemoved(target);
 }
 
 // TODO(mustaq): Make PE drive ME dispatch & bookkeeping in EventHandler.
 WebInputEventResult EventHandler::updatePointerTargetAndDispatchEvents(const AtomicString& mouseEventType, Node* targetNode, int clickCount, const PlatformMouseEvent& mouseEvent)
 {
     ASSERT(mouseEventType == EventTypeNames::mousedown
         || mouseEventType == EventTypeNames::mousemove
         || mouseEventType == EventTypeNames::mouseup);
 
+    // For 4th/5th button in the mouse since Chrome does not yet send
+    // button value to Blink but in some cases it does send the event.
+    // This check is needed to suppress such an event (crbug.com/574959)
+    if (mouseEventType != EventTypeNames::mousemove && mouseEvent.button() == NoButton) {

[dtapuska, 2016/03/23 18:37:31]

braces aren't needed here

+        return WebInputEventResult::HandledSystem;
+    }
+
     updateMouseEventTargetNode(targetNode, mouseEvent);
     if (!m_nodeUnderMouse)
         return WebInputEventResult::NotHandled;
 
     return m_pointerEventManager.sendMousePointerEvent(
         m_nodeUnderMouse, mouseEventType, clickCount, mouseEvent, nullptr,
         m_frame->document()->domWindow());
 }
 
 WebInputEventResult EventHandler::handleMouseFocus(const MouseEventWithHitTestResults& targetedEvent, InputDeviceCapabilities* sourceCapabilities)
@@ skipping 2280 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