Move all knowledge of X sampling into SkScaledCodec

src/codec/SkCodec_libgif.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.
  */
 
 #include "SkCodec.h"
 #include "SkColorTable.h"
 #include "SkImageInfo.h"
@@ skipping 106 matching lines @@
     /*
      * Initializes the swizzler.
      *
      * @param dstInfo  Output image information.  Dimensions may have been
      *                 adjusted if the image frame size does not match the size
      *                 indicated in the header.
      * @param zeroInit Indicates if destination memory is zero initialized.
      */
     Result initializeSwizzler(const SkImageInfo& dstInfo, ZeroInitialized zeroInit);
 
+    SkSampler* getSampler() override { return fSwizzler; }
+
     /*
      * @return kSuccess if the read is successful and kIncompleteInput if the
      *         read fails.
      */
     Result readRow();
 
     Result onStartScanlineDecode(const SkImageInfo& dstInfo, const Options& opts,
                    SkPMColor inputColorPtr[], int* inputColorCount) override;
 
     Result onGetScanlines(void* dst, int count, size_t rowBytes) override;
@@ skipping 31 matching lines @@
     SkAutoTDeleteArray<uint8_t>             fSrcBuffer;
     SkIRect                                 fFrameDims;
     const uint32_t                          fTransIndex;
     uint32_t                                fFillIndex;
     bool                                    fFrameIsSubset;
     SkAutoTDelete<SkSwizzler>               fSwizzler;
     SkAutoTUnref<SkColorTable>              fColorTable;
 
     typedef SkCodec INHERITED;
 };