Don't copy image buffer when calculating size.

src/core/SkImageCacherator.h

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkImageCacherator_DEFINED
 #define SkImageCacherator_DEFINED
 
@@ skipping 51 matching lines @@
      *  formats, so others (e.g. PNG) can just return nullptr.
      */
     SkData* refEncoded(GrContext*);
 
     // Only return true if the generate has already been cached.
     bool lockAsBitmapOnlyIfAlreadyCached(SkBitmap*);
     // Call the underlying generator directly
     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.
     class SharedGenerator final : public SkNVRefCnt<SharedGenerator> {
     public:
         static sk_sp<SharedGenerator> Make(SkImageGenerator* gen) {
             return gen ? sk_sp<SharedGenerator>(new SharedGenerator(gen)) : nullptr;
         }
 
     private:
@@ skipping 33 matching lines @@
     const SkImageInfo      fInfo;
     const SkIPoint         fOrigin;
     const uint32_t         fUniqueID;
 
     friend class GrImageTextureMaker;
     friend class SkImage;
     friend class SkImage_Generator;
 };
 
 #endif