Implement Middle Click Autoscroll on all platforms not just Windows

third_party/WebKit/Source/core/dom/Node.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2008 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
@@ skipping 2054 matching lines @@
         if (dispatchDOMActivateEvent(detail, event) != DispatchEventResult::NotCanceled)
             event->setDefaultHandled();
     } else if (eventType == EventTypeNames::contextmenu) {
         if (Page* page = document().page())
             page->contextMenuController().handleContextMenuEvent(event);
     } else if (eventType == EventTypeNames::textInput) {
         if (event->hasInterface(EventNames::TextEvent)) {
             if (LocalFrame* frame = document().frame())
                 frame->eventHandler().defaultTextInputEventHandler(toTextEvent(event));
         }
-#if OS(WIN)
-    } else if (eventType == EventTypeNames::mousedown && event->isMouseEvent()) {
+    } else if (RuntimeEnabledFeatures::middleClickAutoscrollEnabled()
+        && eventType == EventTypeNames::mousedown
+        && event->isMouseEvent()) {
         MouseEvent* mouseEvent = toMouseEvent(event);
         if (mouseEvent->button() == static_cast<short>(WebPointerProperties::Button::Middle)) {
             if (enclosingLinkEventParentOrSelf())
                 return;
 
             // Avoid that canBeScrolledAndHasScrollableArea changes layout tree
             // structure.
             // FIXME: We should avoid synchronous layout if possible. We can
             // remove this synchronous layout if we avoid synchronous layout in
             // LayoutTextControlSingleLine::scrollHeight
             document().updateStyleAndLayoutIgnorePendingStylesheets();
             LayoutObject* layoutObject = this->layoutObject();
             while (layoutObject && (!layoutObject->isBox() || !toLayoutBox(layoutObject)->canBeScrolledAndHasScrollableArea()))
                 layoutObject = layoutObject->parent();
 
             if (layoutObject) {
                 if (LocalFrame* frame = document().frame())
-                    frame->eventHandler().startPanScrolling(layoutObject);
+                    frame->eventHandler().startMiddleClickAutoscroll(layoutObject);
             }
         }
-#endif
     } else if (event->type() == EventTypeNames::webkitEditableContentChanged) {
         // TODO(chongz): Remove after shipped.
         // New InputEvent are dispatched in Editor::appliedEditing, etc.
         if (!RuntimeEnabledFeatures::inputEventEnabled())
             dispatchInputEvent();
     }
 }
 
 void Node::willCallDefaultEventHandler(const Event&)
 {
@@ skipping 303 matching lines @@
     if (node) {
         std::stringstream stream;
         node->printNodePathTo(stream);
         LOG(INFO) << stream.str();
     } else {
         LOG(INFO) << "Cannot showNodePath for <null>";
     }
 }
 
 #endif