Bug 1469875 - Make nsPluginInstanceOwner::RequestCommitOrCancel() call IMEStateManager::NotifyIME() rather than calling nsIWidget::NotifyIME() r=m_kato

Any content code except TextComposition shouldn't call nsIWidget::NotifyIM()
since IMEStateManager and TextComposition manage state of the composition.
Therefore, we need to make nsPluginInstanceOwner::RequestCommitOrCancel()
call IMEStateManager::NotifyIME() instead.

Additionally, this method should ignore the request if composition has
already been gone.  This patch makes check whether there is a TextComposition
instance for the widget and the composition is handled in the plugin owner
element.

MozReview-Commit-ID: 5cx5X2hGfek

--HG--
extra : rebase_source : 3ff55f877a47ffa74b82af827f1500432b8c272b

dom/plugins/base/nsPluginInstanceOwner.cpp

@@ -892,11 +892,37 @@ nsPluginInstanceOwner::RequestCommitOrCancel(bool aCommitted)
     }
   }
 
-  if (aCommitted) {
-    widget->NotifyIME(widget::REQUEST_TO_COMMIT_COMPOSITION);
-  } else {
-    widget->NotifyIME(widget::REQUEST_TO_CANCEL_COMPOSITION);
+  // Retrieve TextComposition for the widget with IMEStateManager instead of
+  // using GetTextComposition() because we cannot know whether the method
+  // failed due to no widget or no composition.
+  RefPtr<TextComposition> composition =
+    IMEStateManager::GetTextCompositionFor(widget);
+  if (!composition) {
+    // If there is composition, we should just ignore this request since
+    // the composition may have been committed after the plugin process
+    // sent this request.
+    return true;
   }
+
+  nsCOMPtr<nsIContent> content = do_QueryReferent(mContent);
+  if (content != composition->GetEventTargetNode()) {
+    // If the composition is handled in different node, that means that
+    // the composition for the plugin has gone and new composition has
+    // already started.  So, request from the plugin should be ignored
+    // since user inputs different text now.
+    return true;
+  }
+
+  // If active composition is being handled in the plugin, let's request to
+  // commit/cancel the composition via both IMEStateManager and TextComposition
+  // for avoid breaking the status management of composition.  I.e., don't
+  // call nsIWidget::NotifyIME() directly from here.
+  IMEStateManager::NotifyIME(aCommitted ?
+                                widget::REQUEST_TO_COMMIT_COMPOSITION :
+                                widget::REQUEST_TO_CANCEL_COMPOSITION,
+                             widget, composition->GetTabParent());
+  // FYI: This instance may have been destroyed.  Be careful if you need to
+  //      access members of this class.
   return true;
 }