Bug 1359129 - Use the most recent RootDocAccessible when delaying DocAccessibleChild messages. r=aklotz

We sometimes briefly have more than one root DocAccessible associated with a TabChild, for example, while navigating links in a page.  This patch makes sure that we use the correct accessible when delaying messages that we forward to the parent process.

accessible/generic/DocAccessible.cpp

@@ -1481,6 +1481,9 @@ DocAccessible::DoInitialUpdate()
       if (RefPtr<dom::TabChild> tabChild = dom::TabChild::GetFrom(docShell)) {
         DocAccessibleChild* ipcDoc = new DocAccessibleChild(this, tabChild);
         SetIPCDoc(ipcDoc);
+        if (IsRoot()) {
+          tabChild->SetTopLevelDocAccessibleChild(ipcDoc);
+        }
 
 #if defined(XP_WIN)
         IAccessibleHolder holder(CreateHolderFromAccessible(this));

accessible/ipc/win/DocAccessibleChild.cpp

@@ -102,18 +102,8 @@ DocAccessibleChild::PushDeferredEvent(UniquePtr<DeferredEvent> aEvent)
       return;
     }
 
-    nsTArray<PDocAccessibleChild*> ipcDocAccs;
-    tabChild->ManagedPDocAccessibleChild(ipcDocAccs);
-
-    // Look for the top-level DocAccessibleChild - there will only be one
-    // per TabChild.
-    for (uint32_t i = 0, l = ipcDocAccs.Length(); i < l; ++i) {
-      auto ipcDocAcc = static_cast<DocAccessibleChild*>(ipcDocAccs[i]);
-      if (ipcDocAcc->mDoc && ipcDocAcc->mDoc->IsRoot()) {
-        topLevelIPCDoc = ipcDocAcc;
-        break;
-      }
-    }
+    topLevelIPCDoc =
+      static_cast<DocAccessibleChild*>(tabChild->GetTopLevelDocAccessibleChild());
   }
 
   if (topLevelIPCDoc) {

dom/ipc/TabChild.cpp

@@ -403,6 +403,9 @@ TabChild::TabChild(nsIContentChild* aManager,
 #if defined(XP_WIN) && defined(ACCESSIBILITY)
   , mNativeWindowHandle(0)
 #endif
+#if defined(ACCESSIBILITY)
+  , mTopLevelDocAccessibleChild(nullptr)
+#endif
 {
   nsWeakPtr weakPtrThis(do_GetWeakReference(static_cast<nsITabChild*>(this)));  // for capture by the lambda
   mSetAllowedTouchBehaviorCallback = [weakPtrThis](uint64_t aInputBlockId,

dom/ipc/TabChild.h

@@ -675,6 +675,18 @@ public:
 
   mozilla::dom::TabGroup* TabGroup();
 
+#if defined(ACCESSIBILITY)
+  void SetTopLevelDocAccessibleChild(PDocAccessibleChild* aTopLevelChild)
+  {
+    mTopLevelDocAccessibleChild = aTopLevelChild;
+  }
+
+  PDocAccessibleChild* GetTopLevelDocAccessibleChild()
+  {
+    return mTopLevelDocAccessibleChild;
+  }
+#endif
+
 protected:
   virtual ~TabChild();
 
@@ -843,6 +855,10 @@ private:
   uintptr_t mNativeWindowHandle;
 #endif // defined(XP_WIN)
 
+#if defined(ACCESSIBILITY)
+  PDocAccessibleChild* mTopLevelDocAccessibleChild;
+#endif
+
   DISALLOW_EVIL_CONSTRUCTORS(TabChild);
 };