Selectively disable rubber banding on mac.

Source/web/WebInputEventFactoryMac.mm

Index: Source/web/WebInputEventFactoryMac.mm
diff --git a/Source/web/WebInputEventFactoryMac.mm b/Source/web/WebInputEventFactoryMac.mm
index 303fb04ef5001b8fa1fe087a42623e574ce1a283..30e5f2872b795ff58b52857bdea6bc7b52f6d60c 100644
--- a/Source/web/WebInputEventFactoryMac.mm
+++ b/Source/web/WebInputEventFactoryMac.mm
@@ -967,6 +967,11 @@ static WebMouseWheelEvent::Phase momentumPhaseForEvent(NSEvent *event)
 
 WebMouseWheelEvent WebInputEventFactory::mouseWheelEvent(NSEvent* event, NSView* view)
 {
+    return mouseWheelEvent(event, view, true, true);
+}
+
+WebMouseWheelEvent WebInputEventFactory::mouseWheelEvent(NSEvent* event, NSView* view, bool canRubberbandLeft, bool canRubberbandRight)
+{
     WebMouseWheelEvent result;
 
     result.type = WebInputEvent::MouseWheel;
@@ -976,6 +981,9 @@ WebMouseWheelEvent WebInputEventFactory::mouseWheelEvent(NSEvent* event, NSView*
 
     setWebEventLocationFromEventInView(&result, event, view);
 
+    result.canRubberbandLeft = canRubberbandLeft;
+    result.canRubberbandRight = canRubberbandRight;
+
     // Of Mice and Men
     // ---------------
     //