Option for SkCodec to treat dst as all zeroes.

tests/CachedDecodingPixelRefTest.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 "SkBitmap.h"
 #include "SkCachingPixelRef.h"
 #include "SkCanvas.h"
@@ skipping 172 matching lines @@
         if ((NULL == info) || (kFailGetInfo_TestType == fType)) {
             return false;
         }
         *info = SkImageInfo::MakeN32(TestImageGenerator::Width(),
                                      TestImageGenerator::Height(),
                                      kOpaque_SkAlphaType);
         return true;
     }
 
     virtual Result onGetPixels(const SkImageInfo& info, void* pixels, size_t rowBytes,
+                               const Options&,
                                SkPMColor ctable[], int* ctableCount) SK_OVERRIDE {
         REPORTER_ASSERT(fReporter, pixels != NULL);
         REPORTER_ASSERT(fReporter, rowBytes >= info.minRowBytes());
         if (fType != kSucceedGetPixels_TestType) {
             return kUnimplemented;
         }
         if (info.colorType() != kN32_SkColorType) {
             return kInvalidConversion;
         }
         char* bytePtr = static_cast<char*>(pixels);
@@ skipping 144 matching lines @@
         canvas.clear(kDefaultColor);
         canvas.drawImage(image, 0, 0, NULL);
         if (TestImageGenerator::kSucceedGetPixels_TestType == test) {
             REPORTER_ASSERT(
                     r, TestImageGenerator::Color() == *bitmap.getAddr32(0, 0));
         } else {
             REPORTER_ASSERT(r, kDefaultColor == bitmap.getColor(0,0));
         }
     }
 }