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 49 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:
     SkImageCacherator(SkImageGenerator*, const SkImageInfo&, const SkIPoint&, uint32_t uniqueID);
 
     bool generateBitmap(SkBitmap*);
     bool tryLockAsBitmap(SkBitmap*, const SkImage*, SkImage::CachingHint);
 #if SK_SUPPORT_GPU
     // Returns the texture. If the cacherator is generating the texture and wants to cache it,
     // it should use the passed in key (if the key is valid).
     GrTexture* lockTexture(GrContext*, const GrUniqueKey& key, const SkImage* client,
                            SkImage::CachingHint, bool willBeMipped, SkSourceGammaTreatment);
@@ skipping 16 matching lines @@
     SkAutoTDelete<SkImageGenerator> fNotThreadSafeGenerator;
 
     const SkImageInfo   fInfo;
     const SkIPoint      fOrigin;
     const uint32_t      fUniqueID;
 
     friend class GrImageTextureMaker;
 };
 
 #endif