Implement Middle Click Autoscroll on all platforms not just Windows

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

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "core/input/ScrollManager.h"
 
 #include "core/dom/DOMNodeIds.h"
 #include "core/events/GestureEvent.h"
 #include "core/frame/FrameHost.h"
 #include "core/frame/FrameView.h"
@@ skipping 46 matching lines @@
         host->overscrollController().resetAccumulated(resetX, resetY);
     }
 }
 
 void ScrollManager::stopAutoscroll()
 {
     if (AutoscrollController* controller = autoscrollController())
         controller->stopAutoscroll();
 }
 
-bool ScrollManager::panScrollInProgress() const
+bool ScrollManager::middleClickAutoscrollInProgress() const
 {
-    return autoscrollController() && autoscrollController()->panScrollInProgress();
+    return autoscrollController() && autoscrollController()->middleClickAutoscrollInProgress();
 }
 
 AutoscrollController* ScrollManager::autoscrollController() const
 {
     if (Page* page = m_frame->page())
         return &page->autoscrollController();
     return nullptr;
 }
 
 void ScrollManager::recomputeScrollChain(const Node& startNode,
@@ skipping 423 matching lines @@
 DEFINE_TRACE(ScrollManager)
 {
     visitor->trace(m_frame);
     visitor->trace(m_scrollGestureHandlingNode);
     visitor->trace(m_previousGestureScrolledNode);
     visitor->trace(m_scrollbarHandlingScrollGesture);
     visitor->trace(m_resizeScrollableArea);
 }
 
 } // namespace blink