Expose scroll customization for touch to JS (behind REF).

Source/core/page/EventHandler.cpp

Index: Source/core/page/EventHandler.cpp
diff --git a/Source/core/page/EventHandler.cpp b/Source/core/page/EventHandler.cpp
index a2b496fd310859ff0c1de523d186a44af69d7f01..08fad34d180c0f8e33b04c58c2acab115d353aed 100644
--- a/Source/core/page/EventHandler.cpp
+++ b/Source/core/page/EventHandler.cpp
@@ -206,8 +206,12 @@ void recomputeScrollChain(const LocalFrame& frame, const Node& startNode,
     while (curBox && !curBox->isLayoutView()) {
         Node* curNode = curBox->node();
         // FIXME: this should reject more elements, as part of crbug.com/410974.
-        if (curNode && curNode->isElementNode())
-            scrollChain.prepend(toElement(curNode));
+        if (curNode && curNode->isElementNode()) {
+            Element* curElement = toElement(curNode);
+            if (curElement == frame.document()->documentElement())

[Rick Byers, 2015/04/10 14:51:44]

why doesn't the documentElement get put on the scroll chain?  You can customize
both the documentElement and body, right?

[tdresser, 2015/05/08 18:23:02]

I've clarified this in a comment. This only matters in quirks mode.

+                break;
+            scrollChain.prepend(curElement);
+        }
         curBox = curBox->containingBlock();
     }
 
@@ -311,9 +315,8 @@ void EventHandler::clear()
     m_targetForTouchID.clear();
     m_touchSequenceDocument.clear();
     m_touchSequenceUserGestureToken.clear();
-    m_scrollGestureHandlingNode = nullptr;
+    clearGestureScrollState();
     m_lastGestureScrollOverWidget = false;
-    m_previousGestureScrolledNode = nullptr;
     m_scrollbarHandlingScrollGesture = nullptr;
     m_maxMouseMovedDuration = 0;
     m_touchPressed = false;
@@ -2604,7 +2607,7 @@ bool EventHandler::handleGestureScrollEnd(const PlatformGestureEvent& gestureEve
         }
     }
 
-    clearGestureScrollNodes();
+    clearGestureScrollState();
     return false;
 }
 
@@ -2731,7 +2734,7 @@ bool EventHandler::handleGestureScrollUpdate(const PlatformGestureEvent& gesture
     return false;
 }
 
-void EventHandler::clearGestureScrollNodes()
+void EventHandler::clearGestureScrollState()
 {
     m_scrollGestureHandlingNode = nullptr;
     m_previousGestureScrolledNode = nullptr;