SkImage method for detecting lazy decoding

include/core/SkPixelRef.h

Index: include/core/SkPixelRef.h
diff --git a/include/core/SkPixelRef.h b/include/core/SkPixelRef.h
index 5d1aef7dd064e8b6ff789f551ee575ba4a0a74b8..0d9182aae1bf41964771f6b196c04bc18a6a7c95 100644
--- a/include/core/SkPixelRef.h
+++ b/include/core/SkPixelRef.h
@@ -265,6 +265,11 @@ public:
 
     virtual SkDiscardableMemory* diagnostic_only_getDiscardable() const { return NULL; }
 
+    /**
+     *  Returns true if the pixels are generated on-the-fly (when required).
+     */
+    bool isLazyGenerated() const { return this->onIsLazyGenerated(); }
+
 protected:
     /**
      *  On success, returns true and fills out the LockRec for the pixels. On
@@ -318,6 +323,8 @@ protected:
 
     virtual bool onRequestLock(const LockRequest&, LockResult*);
 
+    virtual bool onIsLazyGenerated() const { return false; }
+
     /** Return the mutex associated with this pixelref. This value is assigned
         in the constructor, and cannot change during the lifetime of the object.
     */