Add scanline decoding to SkCodec.

src/codec/SkSwizzler.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 "SkCodecPriv.h"
 #include "SkColorPriv.h"
 #include "SkSwizzler.h"
@@ skipping 245 matching lines @@
     }
     return alphaMask != 0xFF;
 }
 */
 
 SkSwizzler* SkSwizzler::CreateSwizzler(SkSwizzler::SrcConfig sc,
                                        const SkPMColor* ctable,
                                        const SkImageInfo& info, void* dst,
                                        size_t dstRowBytes,
                                        SkImageGenerator::ZeroInitialized zeroInit) {
-    if (kUnknown_SkColorType == info.colorType()) {
+    if (info.colorType() == kUnknown_SkColorType || kUnknown == sc) {
         return NULL;
     }
     if (info.minRowBytes() > dstRowBytes) {
         return  NULL;
     }
     if ((kIndex == sc || kIndex4 == sc || kIndex2 == sc || kIndex1 == sc)
             && NULL == ctable) {
         return NULL;
     }
     RowProc proc = NULL;
@@ skipping 122 matching lines @@
     , fDstInfo(info)
     , fDstRow(dst)
     , fDstRowBytes(rowBytes)
     , fCurrY(0)
 {
     SkDEBUGCODE(fNextMode = kUninitialized_NextMode);
 }
 
 SkSwizzler::ResultAlpha SkSwizzler::next(const uint8_t* SK_RESTRICT src) {
     SkASSERT(0 <= fCurrY && fCurrY < fDstInfo.height());
+    SkASSERT(fDstRow != NULL);
     SkASSERT(kDesignateRow_NextMode != fNextMode);
     SkDEBUGCODE(fNextMode = kConsecutive_NextMode);
 
     // Decode a row
     const ResultAlpha result = fRowProc(fDstRow, src, fDstInfo.width(),
             fDeltaSrc, fCurrY, fColorTable);
 
     // Move to the next row and return the result
+    fCurrY++;
     fDstRow = SkTAddOffset<void>(fDstRow, fDstRowBytes);
     return result;
 }
 
 SkSwizzler::ResultAlpha SkSwizzler::next(const uint8_t* SK_RESTRICT src,
         int y) {
     SkASSERT(0 <= y && y < fDstInfo.height());
     SkASSERT(kConsecutive_NextMode != fNextMode);
     SkDEBUGCODE(fNextMode = kDesignateRow_NextMode);
     
     // Choose the row
     void* row = SkTAddOffset<void>(fDstRow, y*fDstRowBytes);
 
     // Decode the row
     return fRowProc(row, src, fDstInfo.width(), fDeltaSrc, fCurrY,
             fColorTable);
 }