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 "SkCodecPriv.h"
 #include "SkColorPriv.h"
@@ skipping 345 matching lines @@
         return false;
     }
     if (A.alphaType() == B.alphaType()) {
         return true;
     }
     return premul_and_unpremul(A.alphaType(), B.alphaType())
             || premul_and_unpremul(B.alphaType(), A.alphaType());
 }
 
 SkCodec::Result SkPngCodec::onGetPixels(const SkImageInfo& requestedInfo, void* dst,
-                                        size_t rowBytes, SkPMColor ctable[],
-                                        int* ctableCount) {
+                                        size_t rowBytes, const Options& options,
+                                        SkPMColor ctable[], int* ctableCount) {
     if (!this->rewindIfNeeded()) {
         return kCouldNotRewind;
     }
     if (requestedInfo.dimensions() != this->getOriginalInfo().dimensions()) {
         return kInvalidScale;
     }
     if (!conversion_possible(requestedInfo, this->getOriginalInfo())) {
         return kInvalidConversion;
     }
 
@@ skipping 45 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,
+                                              options.fZeroInitialized));
     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;
 }