Use the setting to determine whether showing context menu on mouse up.

Source/core/page/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 2809 matching lines @@
 #endif
 
     PlatformMouseEvent mouseEvent(position, globalPosition, RightButton, eventType, 1, false, false, false, false, PlatformMouseEvent::RealOrIndistinguishable, WTF::currentTime());
 
     handleMousePressEvent(mouseEvent);
     return sendContextMenuEvent(mouseEvent);
 }
 
 bool EventHandler::sendContextMenuEventForGesture(const GestureEventWithHitTestResults& targetedEvent)
 {
-#if OS(WIN)
-    PlatformEvent::Type eventType = PlatformEvent::MouseReleased;
-#else
     PlatformEvent::Type eventType = PlatformEvent::MousePressed;
-#endif
+
+    if (m_frame->settings()->showContextMenuOnMouseUp())
+        eventType = PlatformEvent::MouseReleased;

[Rick Byers, 2014/12/03 13:50:19]

Note to other reviewers:  I didn't bother asking for a test for this gesture
(touch) case because zino@ is just about to land
https://codereview.chromium.org/727593003/ which includes more thorough testing
that will include this scenario.

 
     PlatformMouseEvent mouseEvent(targetedEvent.event().position(), targetedEvent.event().globalPosition(), RightButton, eventType, 1, false, false, false, false, PlatformMouseEvent::FromTouch, WTF::currentTime());
     // To simulate right-click behavior, we send a right mouse down and then
     // context menu event.
     // FIXME: Send HitTestResults to avoid redundant hit tests.
     handleMousePressEvent(mouseEvent);
     return sendContextMenuEvent(mouseEvent);
     // We do not need to send a corresponding mouse release because in case of
     // right-click, the context menu takes capture and consumes all events.
 }
@@ skipping 1017 matching lines @@
 unsigned EventHandler::accessKeyModifiers()
 {
 #if OS(MACOSX)
     return PlatformEvent::CtrlKey | PlatformEvent::AltKey;
 #else
     return PlatformEvent::AltKey;
 #endif
 }
 
 } // namespace blink