Purge cached resources on SkImage destruction.

src/image/SkImage_Base.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 SkImage_Base_DEFINED
 #define SkImage_Base_DEFINED
 
+#include "SkAtomics.h"
 #include "SkImage.h"
 #include "SkSurface.h"
 
 #include <new>
 
 enum {
     kNeedNewImageUniqueID = 0
 };
 
-static SkSurfaceProps copy_or_safe_defaults(const SkSurfaceProps* props) {
-    return props ? *props : SkSurfaceProps(0, kUnknown_SkPixelGeometry);
-}
-
 class SkImage_Base : public SkImage {
 public:
-    SkImage_Base(int width, int height, uint32_t uniqueID, const SkSurfaceProps* props)
-        : INHERITED(width, height, uniqueID)
-        , fProps(copy_or_safe_defaults(props))
-    {}
+    SkImage_Base(int width, int height, uint32_t uniqueID, const SkSurfaceProps* props);
+    virtual ~SkImage_Base();
 
     /**
      *  If the props weren't know at constructor time, call this but only before the image is
      *  ever released into the wild (since the props field must appear to be immutable).
      */
     void initWithProps(const SkSurfaceProps& props) {
         SkASSERT(this->unique());   // only viewed by one thread
         SkSurfaceProps* mutableProps = const_cast<SkSurfaceProps*>(&fProps);
         SkASSERT(mutableProps != &props);   // check for self-assignment
         mutableProps->~SkSurfaceProps();
@@ skipping 27 matching lines @@
 
     // newWidth > 0, newHeight > 0, subset either nullptr or a proper subset of this bounds
     virtual SkImage* onNewImage(int newWidth, int newHeight, const SkIRect* subset,
                                 SkFilterQuality) const;
     virtual SkData* onRefEncoded() const { return nullptr; }
 
     virtual bool onAsLegacyBitmap(SkBitmap*, LegacyBitmapMode) const;
 
     virtual bool onIsLazyGenerated() const { return false; }
 
+    // Call when this image is part of the key to a resourcecache entry. This allows the cache
+    // to know automatically those entries can be purged when this SkImage deleted.
+    void notifyAddedToCache() const {
+        fAddedToCache.store(true);
+    }
+
 private:
     const SkSurfaceProps fProps;
 
+    // Set true by caches when they cache content that's derived from the current pixels.
+    mutable SkAtomic<bool> fAddedToCache;
+
     typedef SkImage INHERITED;
 };
 
 static inline SkImage_Base* as_IB(SkImage* image) {
     return static_cast<SkImage_Base*>(image);
 }
 
 static inline const SkImage_Base* as_IB(const SkImage* image) {
     return static_cast<const SkImage_Base*>(image);
 }
 
 #endif