bug 1196460 - remove proxy's ids when they are destroyed r=surkov

accessible/windows/msaa/AccessibleWrap.cpp

@@ -60,8 +60,6 @@ static gAccessibles = 0;
 
 #ifdef _WIN64
 IDSet AccessibleWrap::sIDGen;
-
-static const uint32_t kNoID = 0;
 #endif
 
 static const int32_t kIEnumVariantDisconnected = -1;

accessible/windows/msaa/AccessibleWrap.h

@@ -177,6 +177,11 @@ public: // construction, destruction
 
   static IDispatch* NativeAccessible(Accessible* aAccessible);
 
+#ifdef _WIN64
+  uint32_t GetExistingID() const { return mID; }
+  static const uint32_t kNoID = 0;
+#endif
+
 protected:
   virtual ~AccessibleWrap();
 

accessible/windows/msaa/Platform.cpp

@@ -59,6 +59,17 @@ a11y::ProxyDestroyed(ProxyAccessible* aProxy)
   if (!wrapper)
     return;
 
+  auto doc =
+    static_cast<DocProxyAccessibleWrap*>(WrapperFor(aProxy->Document()));
+#ifdef _WIN64
+  uint32_t id = wrapper->GetExistingID();
+  if (id != AccessibleWrap::kNoID) {
+    doc->RemoveID(id);
+  }
+#else
+  doc->RemoveID(-reinterpret_cast<int32_t>(wrapper));
+#endif
+
   wrapper->Shutdown();
   aProxy->SetWrapper(0);
   wrapper->Release();