Swipes occur in the wrong direction in RTL

Swipes occur in the wrong direction in RTL
https://bugs.webkit.org/show_bug.cgi?id=143257
<rdar://problem/20300862>

Reviewed by Simon Fraser.

* UIProcess/ios/ViewGestureControllerIOS.mm:
(-[WKSwipeTransitionController gestureRecognizerForInteractiveTransition:WithTarget:action:]):
When choosing which edge to attach our gesture recognizers to,
flip them in RTL.

(-[WKSwipeTransitionController directionForTransition:]):
(WebKit::ViewGestureController::beginSwipeGesture):
(WebKit::ViewGestureController::canSwipeInDirection):
* UIProcess/mac/ViewGestureController.h:
* UIProcess/mac/ViewGestureControllerMac.mm:
(WebKit::ViewGestureController::scrollEventCanBecomeSwipe):
(WebKit::ViewGestureController::trackSwipeGesture):
(WebKit::ViewGestureController::determineLayerAdjacentToSnapshotForParent):
(WebKit::ViewGestureController::beginSwipeGesture):
(WebKit::ViewGestureController::handleSwipeGesture):
Adjust SwipeDirection to be in logical back-forward list direction
instead of physical edge direction.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@182214 268f45cc-cd09-0410-ab3c-d52691b4dbfc