Option for SkCodec to treat dst as all zeroes.

src/images/SkDecodingImageGenerator.cpp

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkData.h"
 #include "SkDecodingImageGenerator.h"
 #include "SkImageDecoder.h"
@@ skipping 25 matching lines @@
                            int sampleSize,
                            bool ditherImage);
 
 protected:
     SkData* onRefEncodedData() SK_OVERRIDE;
     bool onGetInfo(SkImageInfo* info) SK_OVERRIDE {
         *info = fInfo;
         return true;
     }
     virtual Result onGetPixels(const SkImageInfo& info,
-                               void* pixels, size_t rowBytes,
+                               void* pixels, size_t rowBytes, const Options&,
                                SkPMColor ctable[], int* ctableCount) SK_OVERRIDE;
     virtual bool onGetYUV8Planes(SkISize sizes[3], void* planes[3], size_t rowBytes[3],
                                  SkYUVColorSpace* colorSpace) SK_OVERRIDE;
 
 private:
     typedef SkImageGenerator INHERITED;
 };
 
 /**
  *  Special allocator used by getPixels(). Uses preallocated memory
@@ skipping 84 matching lines @@
         }
         size_t length = fStream->getLength();
         if (length) {
             fData = SkData::NewFromStream(fStream, length);
         }
     }
     return SkSafeRef(fData);
 }
 
 SkImageGenerator::Result DecodingImageGenerator::onGetPixels(const SkImageInfo& info,
-        void* pixels, size_t rowBytes, SkPMColor ctableEntries[], int* ctableCount) {
+        void* pixels, size_t rowBytes, const Options& options, SkPMColor ctableEntries[],
+        int* ctableCount) {
     if (fInfo != info) {
         // The caller has specified a different info.  This is an
         // error for this kind of SkImageGenerator.  Use the Options
         // to change the settings.
         if (info.dimensions() != fInfo.dimensions()) {
             return kInvalidScale;
         }
         return kInvalidConversion;
     }
 
@@ skipping 128 matching lines @@
 
 SkImageGenerator* SkDecodingImageGenerator::Create(
         SkStreamRewindable* stream,
         const SkDecodingImageGenerator::Options& opts) {
     SkASSERT(stream != NULL);
     if (stream == NULL) {
         return NULL;
     }
     return CreateDecodingImageGenerator(NULL, stream, opts);
 }