Adding png scanline decoding to kIndex8

tests/CodexTest.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 "Resources.h"
 #include "SkBitmap.h"
 #include "SkCodec.h"
@@ skipping 50 matching lines @@
     bm.eraseColor(SK_ColorYELLOW);
 
     result =
         codec->getPixels(info, bm.getPixels(), bm.rowBytes(), NULL, NULL, NULL);
 
     REPORTER_ASSERT(r, result == SkImageGenerator::kSuccess);
     // verify that re-decoding gives the same result.
     md5(bm, &digest2);
     REPORTER_ASSERT(r, digest1 == digest2);
 
-    SkScanlineDecoder* scanlineDecoder = codec->getScanlineDecoder(info);
+    SkScanlineDecoder* scanlineDecoder = codec->getScanlineDecoder(info, NULL, NULL, NULL);
     if (supportsScanlineDecoding) {
         bm.eraseColor(SK_ColorYELLOW);
         REPORTER_ASSERT(r, scanlineDecoder);
         for (int y = 0; y < info.height(); y++) {
             result = scanlineDecoder->getScanlines(bm.getAddr(0, y), 1, 0);
             REPORTER_ASSERT(r, result == SkImageGenerator::kSuccess);
         }
         // verify that scanline decoding gives the same result.
         SkMD5::Digest digest3;
         md5(bm, &digest3);
@@ skipping 109 matching lines @@
     // JPG
     test_dimensions(r, "CMYK.jpg");
     test_dimensions(r, "color_wheel.jpg");
     test_dimensions(r, "grayscale.jpg");
     test_dimensions(r, "mandrill_512_q075.jpg");
     test_dimensions(r, "randPixels.jpg");
 }