Add an option on SkImageDecoder to skip writing 0s.

bench/SkipZeroesBench.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 "SkBenchmark.h"
 #include "SkBitmap.h"
 #include "SkData.h"
@@ skipping 43 matching lines @@
         if (fValid) {
             const size_t size = fileStream.getLength();
             void* data = sk_malloc_throw(size);
             if (fileStream.read(data, size) < size) {
                 fValid = false;
             } else {
                 SkAutoTUnref<SkData> skdata(SkData::NewFromMalloc(data, size));
                 fStream.setData(skdata.get());
                 fDecoder.reset(SkImageDecoder::Factory(&fStream));
                 if (fDecoder.get()) {
-                    // Disabling until the feature is checked in.
-                    // See https://codereview.chromium.org/24269006/
-                    //fDecoder->setSkipWritingZeroes(fSkipZeroes);
-                    if (fSkipZeroes) {
-                        // This printf will never happen since this bench is
-                        // only currently created with false. Remove once
-                        // the above code is uncommented.
-                        SkDebugf("Should be skipping zeroes...\n");
-                    }
+                    fDecoder->setSkipWritingZeroes(fSkipZeroes);
                 } else {
                     fValid = false;
                 }
             }
         }
     }
 
     virtual void onDraw(SkCanvas*) SK_OVERRIDE {
         if (!fValid) {
 #ifdef SK_DEBUG
@@ skipping 27 matching lines @@
     SkAutoTDelete<SkImageDecoder>   fDecoder;
     const SkString                  fFilename;
     SkMemoryStream                  fStream;
     bool                            fSkipZeroes;
     bool                            fValid;
 
     typedef SkBenchmark INHERITED;
 };
 
 // Enable the true version once the feature is checked in.
-//DEF_BENCH( return SkNEW_ARGS(SkipZeroesBench, ("arrow.png", true)));
+DEF_BENCH( return SkNEW_ARGS(SkipZeroesBench, ("arrow.png", true)));
 DEF_BENCH( return SkNEW_ARGS(SkipZeroesBench, ("arrow.png", false)));