The key for SkBitmapCache can now be genID+SkIRect

src/core/SkBitmapCache.h

Index: src/core/SkBitmapCache.h
diff --git a/src/core/SkBitmapCache.h b/src/core/SkBitmapCache.h
index 9291ff57027ee8ae42fea801bbbb7e20232595f2..cd644fff03ee51f101e17fb9bbfa4e951cf2624d 100644
--- a/src/core/SkBitmapCache.h
+++ b/src/core/SkBitmapCache.h
@@ -31,7 +31,7 @@ public:
      *  result must be marked isImmutable()
      */
     static void Add(const SkBitmap& src, SkScalar invScaleX, SkScalar invScaleY,
-                    const SkBitmap& result);
+            const SkBitmap& result);
 
     /**
      *  Search based on the bitmap's genID, width, height. If found, returns true and
@@ -39,10 +39,24 @@ public:
      */
     static bool Find(uint32_t genID, int width, int height, SkBitmap* result);
 
-    /*
-     *  result must be marked isImmutable()
+    /**
+     * The width and the height provided for the key must be the same as the result bitmap ones.
+     *
+     * result must be marked isImmutable()
+     */
+    static bool Add(uint32_t genID, int width, int height, const SkBitmap& result);
+
+    /**
+     *  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);
+
+    /**
+     * The width and the height of the provided subset must be the same as the result bitmap ones.
+     * result must be marked isImmutable()
      */
-    static void Add(uint32_t genID, int width, int height, const SkBitmap& result);
+    static bool Add(uint32_t genID, const SkIRect& subset, const SkBitmap& result);
 };
 
 class SkMipMapCache {