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..d1f4cf16c6ec66debaf1f60edfbf09001593a12d 100644
--- a/Source/web/WebInputEventFactoryMac.mm
+++ b/Source/web/WebInputEventFactoryMac.mm
@@ -965,7 +965,7 @@ static WebMouseWheelEvent::Phase momentumPhaseForEvent(NSEvent *event)
     return phaseForNSEventPhase(eventMomentumPhase);
 }
 
-WebMouseWheelEvent WebInputEventFactory::mouseWheelEvent(NSEvent* event, NSView* view)
+WebMouseWheelEvent WebInputEventFactory::mouseWheelEvent(NSEvent* event, NSView* view, bool canRubberbandLeft, bool canRubberbandRight)
 {
     WebMouseWheelEvent result;
 
@@ -976,6 +976,9 @@ WebMouseWheelEvent WebInputEventFactory::mouseWheelEvent(NSEvent* event, NSView*
 
     setWebEventLocationFromEventInView(&result, event, view);
 
+    result.canRubberbandLeft = canRubberbandLeft;
+    result.canRubberbandRight = canRubberbandRight;
+
     // Of Mice and Men
     // ---------------
     //