allow SkBitmapCache to operate on a local instance, for testability

src/core/SkBitmapCache.h

Index: src/core/SkBitmapCache.h
diff --git a/src/core/SkBitmapCache.h b/src/core/SkBitmapCache.h
index aec7a7d41cb6fd906e2eb2a458460bd5f6152701..181c85812aa86ae8e14fb7d66b54af5c700b59ce 100644
--- a/src/core/SkBitmapCache.h
+++ b/src/core/SkBitmapCache.h
@@ -11,6 +11,7 @@
 #include "SkScalar.h"
 #include "SkBitmap.h"
 
+class SkResourceCache;
 class SkMipMap;
 
 class SkBitmapCache {
@@ -25,25 +26,28 @@ public:
      *  Search based on the src bitmap and inverse scales in X and Y. If found, returns true and
      *  result will be set to the matching bitmap with its pixels already locked.
      */
-    static bool Find(const SkBitmap& src, SkScalar invScaleX, SkScalar invScaleY, SkBitmap* result);
+    static bool Find(const SkBitmap& src, SkScalar invScaleX, SkScalar invScaleY, SkBitmap* result,
+                     SkResourceCache* localCache = NULL);
 
     /*
      *  result must be marked isImmutable()
      */
     static void Add(const SkBitmap& src, SkScalar invScaleX, SkScalar invScaleY,
-            const SkBitmap& result);
+            const SkBitmap& result, SkResourceCache* localCache = NULL);
 
     /**
      *  Search based on the bitmap's genID and subset. If found, returns true and
      *  result will be set to the matching bitmap with its pixels already locked.
      */
-    static bool Find(uint32_t genID, const SkIRect& subset, SkBitmap* result);
+    static bool Find(uint32_t genID, const SkIRect& subset, SkBitmap* result,
+                     SkResourceCache* localCache = NULL);
 
     /**
      * The width and the height of the provided subset must be the same as the result bitmap ones.
      * result must be marked isImmutable()
      */
-    static bool Add(uint32_t genID, const SkIRect& subset, const SkBitmap& result);
+    static bool Add(uint32_t genID, const SkIRect& subset, const SkBitmap& result,
+                    SkResourceCache* localCache = NULL);
 };
 
 class SkMipMapCache {