Implement touch-action pan-x/pan-y handling on the main thread

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
old mode 100644
new mode 100755
index 24b02a8368b3bdeed6d7d9d685d4feb0c5e91130..92c5fb8b3023b211ce90afc731b597c5499bbc00
--- a/Source/core/page/EventHandler.cpp
+++ b/Source/core/page/EventHandler.cpp
@@ -3903,6 +3903,19 @@ bool EventHandler::handleWheelEventAsEmulatedGesture(const PlatformWheelEvent& e
     return true;
 }
 
+TouchAction EventHandler::intersectTouchAction(TouchAction action, TouchAction effectiveTouchAction)

[Rick Byers, 2013/12/13 22:17:35]

nit: since the two parameters are equivalent (the function is symmetric on it's
inputs) I'd just call them 'action1' and 'action2'.  This makes it feel to me
like there's something special about the 2nd arg.

[gnana, 2013/12/16 11:41:09]

Done.

+{
+    if (action == TouchActionNone || effectiveTouchAction == TouchActionNone)
+        return TouchActionNone;
+    if (action == TouchActionAuto)
+        return effectiveTouchAction;
+    if (effectiveTouchAction == TouchActionAuto)
+        return action;
+    if (!(action & effectiveTouchAction))
+        return TouchActionNone;
+    return action & effectiveTouchAction;
+}
+
 TouchAction EventHandler::computeEffectiveTouchAction(const Node& node)
 {
     // Optimization to minimize risk of this new feature (behavior should be identical
@@ -3914,13 +3927,16 @@ TouchAction EventHandler::computeEffectiveTouchAction(const Node& node)
     // the target node up to the nearest scrollable ancestor and exclude any
     // prohibited actions. For now this is trivial, but when we add more types
     // of actions it'll get a little more complex.
+    TouchAction effectiveTouchAction = TouchActionAuto;
     for (const Node* curNode = &node; curNode; curNode = NodeRenderingTraversal::parent(curNode)) {
         // The spec says only block and SVG elements get touch-action.
         // FIXME(rbyers): Add correct support for SVG, crbug.com/247396.
         if (RenderObject* renderer = curNode->renderer()) {
             if (renderer->isRenderBlockFlow()) {
-                if (renderer->style()->touchAction() == TouchActionNone)
-                    return TouchActionNone;
+                TouchAction action = renderer->style()->touchAction();
+                effectiveTouchAction = intersectTouchAction(action, effectiveTouchAction);
+                if (effectiveTouchAction == TouchActionNone)
+                    break;
             }
 
             // If we've reached an ancestor that supports a touch action, search no further.
@@ -3928,7 +3944,7 @@ TouchAction EventHandler::computeEffectiveTouchAction(const Node& node)
                 break;
         }
     }
-    return TouchActionAuto;
+    return effectiveTouchAction;
 }
 
 void EventHandler::setLastKnownMousePosition(const PlatformMouseEvent& event)