Reintroduce support for the CGImage destruction listener. (#2099)

Fixes #1928.
Fixes #2096.
Refs #2098.

Author: DHowett

Frameworks/CoreGraphics/CGImage.mm

@@ -39,15 +39,13 @@
 
 static const wchar_t* TAG = L"CGImage";
 
-// TODO #1124: remove old code
-#pragma region OLD_CODE
+// This is used by XamlCompositor to flush the DisplayTexture cache.
+// TODO GH#2098 look at where we're using the image cache and what we can do to avoid it.
 static std::vector<CGImageDestructionListener> _imageDestructionListeners;
 COREGRAPHICS_EXPORT void CGImageAddDestructionListener(CGImageDestructionListener listener) {
     _imageDestructionListeners.push_back(listener);
 }
 
-#pragma endregion OLD_CODE
-
 #pragma region CGImageImplementation
 
 struct __CGImageImpl {
@@ -225,6 +223,12 @@ inline WICPixelFormatGUID PixelFormat() const {
         _impl.renderingIntent = intent;
         return *this;
     }
+
+    ~__CGImage() {
+        for (auto listener: _imageDestructionListeners) {
+            listener(this);
+        }
+    }
 };
 
 #pragma endregion CGImageImplementation