add callbacks to Images that wrap client-provided content

include/gpu/GrSurface.h

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 
 #ifndef GrSurface_DEFINED
 #define GrSurface_DEFINED
@@ skipping 109 matching lines @@
     /**
      * After this returns any pending writes to the surface will be issued to the backend 3D API and
      * if the surface has MSAA it will be resolved.
      */
     void prepareForExternalRead();
     
     /** Access methods that are only to be used within Skia code. */
     inline GrSurfacePriv surfacePriv();
     inline const GrSurfacePriv surfacePriv() const;
 
+    typedef void* ReleaseCtx;
+    typedef void (*ReleaseProc)(ReleaseCtx);
+    
+    void setRelease(ReleaseProc proc, ReleaseCtx ctx) {
+        fReleaseProc = proc;
+        fReleaseCtx = ctx;
+    }
+
 protected:
     // Methods made available via GrSurfacePriv
     SkImageInfo info() const;
     bool savePixels(const char* filename);
     bool hasPendingRead() const;
     bool hasPendingWrite() const;
     bool hasPendingIO() const;
 
     // Provides access to methods that should be public within Skia code.
     friend class GrSurfacePriv;
 
     GrSurface(GrGpu* gpu, LifeCycle lifeCycle, const GrSurfaceDesc& desc)
         : INHERITED(gpu, lifeCycle)
-        , fDesc(desc) {
+        , fDesc(desc)
+        , fReleaseProc(NULL)
+        , fReleaseCtx(NULL)
+    {}
+
+    ~GrSurface() override {
+        // check that invokeReleaseProc has been called (if needed)
+        SkASSERT(NULL == fReleaseProc);
     }
 
     GrSurfaceDesc fDesc;
 
+    void onRelease() override;
+    void onAbandon() override;
+
 private:
+    void invokeReleaseProc() {
+        if (fReleaseProc) {
+            fReleaseProc(fReleaseCtx);
+            fReleaseProc = NULL;
+        }
+    }
+    
+    ReleaseProc fReleaseProc;
+    ReleaseCtx  fReleaseCtx;
+
     typedef GrGpuResource INHERITED;
 };
 
 #endif