Bug 1264852 - destroy an event tree as it gets processed, r=n.nethercote

accessible/base/EventTree.cpp

@@ -183,13 +183,12 @@ TreeMutation::Done()
 void
 EventTree::Process()
 {
-  EventTree* node = mFirst;
-  while (node) {
+  while (mFirst) {
     // Skip a node and its subtree if its container is not in the document.
-    if (node->mContainer->IsInDocument()) {
-      node->Process();
+    if (mFirst->mContainer->IsInDocument()) {
+      mFirst->Process();
     }
-    node = node->mNext;
+    mFirst = mFirst->mNext.forget();
   }
 
   MOZ_ASSERT(mContainer || mDependentEvents.IsEmpty(),

accessible/base/NotificationController.cpp

@@ -402,7 +402,6 @@ NotificationController::WillRefresh(mozilla::TimeStamp aTime)
   mObservingState = eRefreshProcessing;
 
   mEventTree.Process();
-  mEventTree.Clear();
 
   ProcessEventQueue();