Fix SkGifCodec to handle gifs where frameSize != imageSize

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 66 matching lines @@
      * data.
      *
      * @param gif        Pointer to the library type that manages the gif decode
      * @param transIndex This call will set the transparent index based on the
      *                   extension data.
      */
      static Result ReadUpToFirstImage(GifFileType* gif, uint32_t* transIndex);
 
      /*
       * A gif may contain many image frames, all of different sizes.
-      * This function checks if the frame dimensions are valid and corrects
-      * them if necessary.  It then sets fFrameDims to the corrected
-      * dimensions.
+      * This function checks if the gif dimensions are valid, based on the frame
+      * dimensions, and corrects the gif dimensions if necessary.
       *
-      * @param desc The image frame descriptor
+      * @param gif       Pointer to the library type that manages the gif decode
+      * @param size      Size of the image that we will decode.
+      *                  Will be set by this function if the return value is true.
+      * @param frameRect Contains the dimenions and offset of the first image frame.
+      *                  Will be set by this function if the return value is true.
+      *
+      * @return true on success, false otherwise
       */
-     bool setFrameDimensions(const GifImageDesc& desc);
+     static bool GetDimensions(GifFileType* gif, SkISize* size, SkIRect* frameRect);
 
     /*
      * Initializes the color table that we will use for decoding.
      *
      * @param dstInfo         Contains the requested dst color type.
      * @param inputColorPtr   Copies the encoded color table to the client's
      *                        input color table if the client requests kIndex8.
      * @param inputColorCount If the client requests kIndex8, sets
      *                        inputColorCount to 256.  Since gifs always
      *                        contain 8-bit indices, we need a 256 entry color
@@ skipping 53 matching lines @@
      * Creates an instance of the decoder
      * Called only by NewFromStream
      *
      * @param srcInfo contains the source width and height
      * @param stream the stream of image data
      * @param gif pointer to library type that manages gif decode
      *            takes ownership
      * @param transIndex  The transparent index.  An invalid value
      *            indicates that there is no transparent index.
      */
-    SkGifCodec(const SkImageInfo& srcInfo, SkStream* stream, GifFileType* gif, uint32_t transIndex);
+    SkGifCodec(const SkImageInfo& srcInfo, SkStream* stream, GifFileType* gif, uint32_t transIndex,
+            const SkIRect& frameRect, bool frameIsSubset);
 
     SkAutoTCallVProc<GifFileType, CloseGif> fGif; // owned
     SkAutoTDeleteArray<uint8_t>             fSrcBuffer;
-    SkIRect                                 fFrameDims;
+    const SkIRect                           fFrameRect;
     const uint32_t                          fTransIndex;
     uint32_t                                fFillIndex;
-    bool                                    fFrameIsSubset;
+    const bool                              fFrameIsSubset;
     SkAutoTDelete<SkSwizzler>               fSwizzler;
     SkAutoTUnref<SkColorTable>              fColorTable;
 
     typedef SkCodec INHERITED;
 };