Write transparent pixels more often (SkGifCodec)

third_party/gif/SkGifImageReader.h

 /* -*- Mode: C; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
 /* ***** BEGIN LICENSE BLOCK *****
  * Version: MPL 1.1/GPL 2.0/LGPL 2.1
  *
  * The contents of this file are subject to the Mozilla Public License Version
  * 1.1 (the "License"); you may not use this file except in compliance with
  * the License. You may obtain a copy of the License at
  * http://www.mozilla.org/MPL/
  *
  * Software distributed under the License is distributed on an "AS IS" basis,
@@ skipping 84 matching lines @@
         , codemask(0)
         , clearCode(0)
         , avail(0)
         , oldcode(0)
         , firstchar(0)
         , bits(0)
         , datum(0)
         , ipass(0)
         , irow(0)
         , rowsRemaining(0)
+        , alwaysWriteTransparentPixels(false)
         , rowIter(0)
         , m_client(client)
         , m_frameContext(frameContext)
     { }
 
     bool prepareToDecode();
     bool outputRow(const unsigned char* rowBegin);
     bool doLZW(const unsigned char* block, size_t bytesInBlock);
     bool hasRemainingRows() { return SkToBool(rowsRemaining); }
 
 private:
     // LZW decoding states and output states.
     int codesize;
     int codemask;
     int clearCode; // Codeword used to trigger dictionary reset.
     int avail; // Index of next available slot in dictionary.
     int oldcode;
     unsigned char firstchar;
     int bits; // Number of unread bits in "datum".
     int datum; // 32-bit input buffer.
     int ipass; // Interlace pass; Ranges 1-4 if interlaced.
     size_t irow; // Current output row, starting at zero.
     size_t rowsRemaining; // Rows remaining to be output.
+    // This depends on the GIFFrameContext. If the frame is not
+    // interlaced and it is independent, it is always safe to
+    // write transparent pixels.
+    bool alwaysWriteTransparentPixels;
 
     unsigned short prefix[SK_MAX_DICTIONARY_ENTRIES];
     unsigned char suffix[SK_MAX_DICTIONARY_ENTRIES];
     unsigned short suffixLength[SK_MAX_DICTIONARY_ENTRIES];
     SkGIFRow rowBuffer; // Single scanline temporary buffer.
     unsigned char* rowIter;
 
     SkGifCodec* const m_client;
     const SkGIFFrameContext* m_frameContext;
 };
@@ skipping 252 matching lines @@
     SkStreamBuffer m_streamBuffer;
     bool m_parseCompleted;
 
     // These values can be computed before we create a SkGIFFrameContext, so we
     // store them here instead of on m_frames[0].
     bool m_firstFrameHasAlpha;
     bool m_firstFrameSupportsIndex8;
 };
 
 #endif