Bug 1119133 Implement TextEventDispatcher::EndInputTransaction() for ensuring TextEventDispatcher forgets the link with TextInputProcessor r=smaug

dom/base/TextInputProcessor.cpp

@@ -186,7 +186,14 @@ TextInputProcessor::BeginInputTransactionInternal(
 
   // This instance has finished preparing to link to the dispatcher.  Therefore,
   // let's forget the old dispatcher and purpose.
-  UnlinkFromTextEventDispatcher();
+  if (mDispatcher) {
+    mDispatcher->EndInputTransaction(this);
+    if (NS_WARN_IF(mDispatcher)) {
+      // Forcibly initialize the members if we failed to end the input
+      // transaction.
+      UnlinkFromTextEventDispatcher();
+    }
+  }
 
   if (aForTests) {
     rv = dispatcher->BeginInputTransactionForTests(this);

widget/TextEventDispatcher.cpp

@@ -83,6 +83,26 @@ TextEventDispatcher::BeginInputTransactionInternal(
   return NS_OK;
 }
 
+void
+TextEventDispatcher::EndInputTransaction(TextEventDispatcherListener* aListener)
+{
+  if (NS_WARN_IF(IsComposing()) || NS_WARN_IF(IsDispatchingEvent())) {
+    return;
+  }
+
+  nsCOMPtr<TextEventDispatcherListener> listener = do_QueryReferent(mListener);
+  if (NS_WARN_IF(!listener)) {
+    return;
+  }
+
+  if (NS_WARN_IF(listener != aListener)) {
+    return;
+  }
+
+  mListener = nullptr;
+  listener->OnRemovedFrom(this);
+}
+
 void
 TextEventDispatcher::OnDestroyWidget()
 {

widget/TextEventDispatcher.h

@@ -59,6 +59,14 @@ public:
   nsresult BeginInputTransactionForTests(
              TextEventDispatcherListener* aListener);
 
+  /**
+   * EndInputTransaction() should be called when the listener stops using
+   * the TextEventDispatcher.
+   *
+   * @param aListener       The listener using the TextEventDispatcher instance.
+   */
+  void EndInputTransaction(TextEventDispatcherListener* aListener);
+
   /**
    * OnDestroyWidget() is called when mWidget is being destroyed.
    */