Option for SkCodec to treat dst as all zeroes.

src/codec/SkCodec_libpng.cpp

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkCodec_libpng.h"
 #include "SkColorPriv.h"
 #include "SkColorTable.h"
@@ skipping 415 matching lines @@
         // Note: we check the destination, since otherwise we would have
         // told png to upscale.
         SkASSERT(PNG_COLOR_TYPE_GRAY == pngColorType);
         sc = SkSwizzler::kGray;
     } else if (this->getOriginalInfo().alphaType() == kOpaque_SkAlphaType) {
         sc = SkSwizzler::kRGBX;
     } else {
         sc = SkSwizzler::kRGBA;
     }
     const SkPMColor* colors = colorTable ? colorTable->readColors() : NULL;
-    // TODO: Support skipZeroes.
     swizzler.reset(SkSwizzler::CreateSwizzler(sc, colors, requestedInfo,
-                                              dst, rowBytes, false));
+                                              dst, rowBytes,
+                                              this->getZeroInitialized()));
     if (!swizzler) {
         // FIXME: CreateSwizzler could fail for another reason.
         return kUnimplemented;
     }
 
     // FIXME: Here is where we should likely insert some of the modifications
     // made in the factory.
     png_read_update_info(fPng_ptr, fInfo_ptr);
 
     if (numberPasses > 1) {
@@ skipping 34 matching lines @@
 
     // FIXME: do we need substituteTranspColor?
 
     if (reallyHasAlpha && requestedInfo.alphaType() != kOpaque_SkAlphaType) {
         // FIXME: We want to alert the caller. Is this the right way?
         SkImageInfo* modInfo = const_cast<SkImageInfo*>(&requestedInfo);
         *modInfo = requestedInfo.makeAlphaType(kOpaque_SkAlphaType);
     }
     return kSuccess;
 }