Support decoding opaque to *premul

include/codec/SkCodec.h

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkCodec_DEFINED
 #define SkCodec_DEFINED
 
@@ skipping 552 matching lines @@
      */
     virtual bool onRewind() {
         return true;
     }
 
     /**
      * On an incomplete input, getPixels() and getScanlines() will fill any uninitialized
      * scanlines.  This allows the subclass to indicate what value to fill with.
      *
      * @param colorType Destination color type.
-     * @param alphaType Destination alpha type.
      * @return          The value with which to fill uninitialized pixels.
      *
      * Note that we can interpret the return value as an SkPMColor, a 16-bit 565 color,
      * an 8-bit gray color, or an 8-bit index into a color table, depending on the color
      * type.
      */
-    uint32_t getFillValue(SkColorType colorType, SkAlphaType alphaType) const {
-        return this->onGetFillValue(colorType, alphaType);
+    uint32_t getFillValue(SkColorType colorType) const {
+        return this->onGetFillValue(colorType);
     }
 
     /**
      * Some subclasses will override this function, but this is a useful default for the color
      * types that we support.  Note that for color types that do not use the full 32-bits,
      * we will simply take the low bits of the fill value.
      *
-     * kN32_SkColorType: Transparent or Black
+     * kN32_SkColorType: Transparent or Black, depending on the src alpha type
      * kRGB_565_SkColorType: Black
      * kGray_8_SkColorType: Black
      * kIndex_8_SkColorType: First color in color table
      */
-    virtual uint32_t onGetFillValue(SkColorType /*colorType*/, SkAlphaType alphaType) const {
-        return kOpaque_SkAlphaType == alphaType ? SK_ColorBLACK : SK_ColorTRANSPARENT;
+    virtual uint32_t onGetFillValue(SkColorType /*colorType*/) const {
+        return kOpaque_SkAlphaType == fSrcInfo.alphaType() ? SK_ColorBLACK : SK_ColorTRANSPARENT;
     }
 
     /**
      * Get method for the input stream
      */
     SkStream* stream() {
         return fStream.get();
     }
 
     /**
@@ skipping 91 matching lines @@
      *  not affect ownership.
      *
      *  Only valid during scanline decoding.
      */
     virtual SkSampler* getSampler(bool /*createIfNecessary*/) { return nullptr; }
 
     friend class SkSampledCodec;
     friend class SkIcoCodec;
 };
 #endif // SkCodec_DEFINED