platform/mac/accessibility/aria-multiline.html sometimes asserts in AccessibilityCont...

platform/mac/accessibility/aria-multiline.html sometimes asserts in AccessibilityController::removeNotificationListener
https://bugs.webkit.org/show_bug.cgi?id=127141

Reviewed by Alexey Proskuryakov.

Make sure to reset the notification handler each time.

* DumpRenderTree/AccessibilityController.cpp:
(AccessibilityController::resetToConsistentState):
* DumpRenderTree/AccessibilityController.h:
* DumpRenderTree/atk/AccessibilityControllerAtk.cpp:
(AccessibilityController::platformResetToConsistentState):
* DumpRenderTree/ios/AccessibilityControllerIOS.mm:
(AccessibilityController::platformResetToConsistentState):
* DumpRenderTree/mac/AccessibilityControllerMac.mm:
(AccessibilityController::~AccessibilityController):
(AccessibilityController::platformResetToConsistentState):
(AccessibilityController::removeNotificationListener):
* DumpRenderTree/win/AccessibilityControllerWin.cpp:
(AccessibilityController::platformResetToConsistentState):

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@162222 268f45cc-cd09-0410-ab3c-d52691b4dbfc