Implement Middle Click Autoscroll on all platforms not just Windows

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 c4b8be9bd2429711db21cfc9df3e5f292108c97f..889dd642f6ce00c3d2c160835388ce21979332f3 100644
--- a/third_party/WebKit/Source/core/input/EventHandler.cpp
+++ b/third_party/WebKit/Source/core/input/EventHandler.cpp
@@ -411,7 +411,7 @@ WebInputEventResult EventHandler::handleMouseDraggedEvent(const MouseEventWithHi
 
     m_mouseDownMayStartDrag = false;
 
-    if (m_mouseDownMayStartAutoscroll && !m_scrollManager.panScrollInProgress()) {
+    if (m_mouseDownMayStartAutoscroll && !m_scrollManager.middleClickAutoscrollInProgress()) {
         if (AutoscrollController* controller = m_scrollManager.autoscrollController()) {
             controller->startAutoscrollForSelection(layoutObject);
             m_mouseDownMayStartAutoscroll = false;
@@ -436,8 +436,6 @@ WebInputEventResult EventHandler::handleMouseReleaseEvent(const MouseEventWithHi
     return selectionController().handleMouseReleaseEvent(event, m_dragStartPos) ? WebInputEventResult::HandledSystem : WebInputEventResult::NotHandled;
 }
 
-#if OS(WIN)
-
 void EventHandler::startPanScrolling(LayoutObject* layoutObject)
 {

[bokan, 2016/09/07 16:33:46]

Add a DCHECK for the new RuntimeEnabledFeature here

     if (!layoutObject->isBox())
@@ -449,8 +447,6 @@ void EventHandler::startPanScrolling(LayoutObject* layoutObject)
     invalidateClick();
 }
 
-#endif // OS(WIN)
-
 HitTestResult EventHandler::hitTestResultAtPoint(const LayoutPoint& point, HitTestRequest::HitTestRequestType hitType, const LayoutSize& padding)
 {
     TRACE_EVENT0("blink", "EventHandler::hitTestResultAtPoint");
@@ -601,7 +597,7 @@ OptionalCursor EventHandler::selectCursor(const HitTestResult& result)
     Page* page = m_frame->page();
     if (!page)
         return NoCursorChange;
-    if (m_scrollManager.panScrollInProgress())
+    if (m_scrollManager.middleClickAutoscrollInProgress())
         return NoCursorChange;
 
     Node* node = result.innerPossiblyPseudoNode();
@@ -831,18 +827,18 @@ WebInputEventResult EventHandler::handleMousePressEvent(const PlatformMouseEvent
         return result;
     }
 
-#if OS(WIN)
-    // We store whether pan scrolling is in progress before calling stopAutoscroll()
-    // because it will set m_autoscrollType to NoAutoscroll on return.
-    bool isPanScrollInProgress = m_scrollManager.panScrollInProgress();
-    m_scrollManager.stopAutoscroll();
-    if (isPanScrollInProgress) {
-        // We invalidate the click when exiting pan scrolling so that we don't inadvertently navigate
-        // away from the current page (e.g. the click was on a hyperlink). See <rdar://problem/6095023>.
-        invalidateClick();
-        return WebInputEventResult::HandledSuppressed;
+    if (RuntimeEnabledFeatures::middleClickAutoscrollEnabled()) {
+        // We store whether pan scrolling is in progress before calling stopAutoscroll()
+        // because it will set m_autoscrollType to NoAutoscroll on return.
+        bool isPanScrollInProgress = m_scrollManager.middleClickAutoscrollInProgress();
+        m_scrollManager.stopAutoscroll();
+        if (isPanScrollInProgress) {
+            // We invalidate the click when exiting pan scrolling so that we don't inadvertently navigate
+            // away from the current page (e.g. the click was on a hyperlink). See <rdar://problem/6095023>.
+            invalidateClick();
+            return WebInputEventResult::HandledSuppressed;
+        }
     }
-#endif
 
     m_clickCount = mouseEvent.clickCount();
     m_clickNode = mev.innerNode()->isTextNode() ?  FlatTreeTraversal::parent(*mev.innerNode()) : mev.innerNode();
@@ -1113,10 +1109,10 @@ WebInputEventResult EventHandler::handleMouseReleaseEvent(const PlatformMouseEve
     else
         gestureIndicator = wrapUnique(new UserGestureIndicator(DefinitelyProcessingUserGesture));
 
-#if OS(WIN)
-    if (Page* page = m_frame->page())
-        page->autoscrollController().handleMouseReleaseForPanScrolling(m_frame, mouseEvent);
-#endif
+    if (RuntimeEnabledFeatures::middleClickAutoscrollEnabled()) {
+        if (Page* page = m_frame->page())
+            page->autoscrollController().handleMouseReleaseForPanScrolling(m_frame, mouseEvent);
+    }
 
     m_mousePressed = false;
     setLastKnownMousePosition(mouseEvent);