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 a8a05a1f90b0adbfc6f7d433a83b098f9506b13a..63db2ed6d80d2d68890a1172f1da79508c687e59 100644
--- a/src/core/SkImageCacherator.h
+++ b/src/core/SkImageCacherator.h
@@ -69,6 +69,15 @@ 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:
     // Ref-counted tuple(SkImageGenerator, SkMutex) which allows sharing of one generator
     // among several cacherators.