Trying to add the same scaled image twice shouldn't assert.

src/core/SkScaledImageCache.h

Index: src/core/SkScaledImageCache.h
diff --git a/src/core/SkScaledImageCache.h b/src/core/SkScaledImageCache.h
index fee69d2d58598eb8fee6a7562a45bd2940912e6f..44ef1f8a2cb8e19369452ae191514eb0cdf3b98c 100644
--- a/src/core/SkScaledImageCache.h
+++ b/src/core/SkScaledImageCache.h
@@ -126,6 +126,7 @@ public:
 
 public:
     struct Rec;
+    struct Key;
 private:
     Rec*    fHead;
     Rec*    fTail;
@@ -139,7 +140,8 @@ private:
 
     Rec* findAndLock(uint32_t generationID, SkScalar sx, SkScalar sy,
                      const SkIRect& bounds);
-    void addAndLock(Rec* rec);
+    Rec* findAndLock(const Key& key);
+    ID* addAndLock(Rec* rec);
 
     void purgeAsNeeded();