Don't copy image buffer when calculating size.

src/core/SkImageCacherator.h

Index: src/core/SkImageCacherator.h
diff --git a/src/core/SkImageCacherator.h b/src/core/SkImageCacherator.h
index 3be69a5785686e811e2a0c2e4c151d6cbeeaf95c..9a9cf8d50ae362b346bad73f09289ea4867bca4e 100644
--- a/src/core/SkImageCacherator.h
+++ b/src/core/SkImageCacherator.h
@@ -67,6 +67,15 @@ public:
     bool directGeneratePixels(const SkImageInfo& dstInfo, void* dstPixels, size_t dstRB,
                               int srcX, int srcY);
 
+#if SK_SUPPORT_GPU
+    /**
+     * Returns true if the generate can efficiently return a texture (given the properties of the
+     * proxy). By default, simple codecs will usually return false, since they must be decoded
+     * on the CPU and then uploaded to become a texture.
+     */
+    bool canGenerateTexture(const GrContextThreadSafeProxy& proxy);
+#endif
+
 private:
     SkImageCacherator(SkImageGenerator*, const SkImageInfo&, const SkIPoint&, uint32_t uniqueID);