Rename SkCodec_libpng to SkPngCodec

src/codec/SkCodec.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 "SkBmpCodec.h"
 #include "SkCodec.h"
-#include "SkCodec_libpng.h"
 #include "SkCodecPriv.h"
 #include "SkData.h"
 #include "SkGifCodec.h"
 #include "SkIcoCodec.h"
 #if !defined(GOOGLE3)
 #include "SkJpegCodec.h"
 #endif
+#include "SkPngCodec.h"
 #include "SkStream.h"
 #include "SkWbmpCodec.h"
 #include "SkWebpCodec.h"
 
 struct DecoderProc {
     bool (*IsFormat)(const void*, size_t);
     SkCodec* (*NewFromStream)(SkStream*);
 };
 
 static const DecoderProc gDecoderProcs[] = {
@@ skipping 338 matching lines @@
             SkASSERT(1 == linesRequested || this->getInfo().height() == linesRequested);
             const SkImageInfo fillInfo = info.makeWH(info.width(), 1);
             for (int srcY = linesDecoded; srcY < linesRequested; srcY++) {
                 fillDst = SkTAddOffset<void>(dst, this->outputScanline(srcY) * rowBytes);
                 fill_proc(fillInfo, fillDst, rowBytes, fillValue, zeroInit, sampler);
             }
             break;
         }
     }
 }