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diff --git a/image/decoders/GIF2.h b/image/decoders/GIF2.h
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+++ b/image/decoders/GIF2.h
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+/* -*- Mode: C; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_image_decoders_GIF2_H
+#define mozilla_image_decoders_GIF2_H
+
+#define MAX_LZW_BITS 12
+#define MAX_BITS 4097  // 2^MAX_LZW_BITS+1
+#define MAX_COLORS 256
+#define MIN_HOLD_SIZE 256
+
+enum { GIF_TRAILER = 0x3B };               // ';'
+enum { GIF_IMAGE_SEPARATOR = 0x2C };       // ','
+enum { GIF_EXTENSION_INTRODUCER = 0x21 };  // '!'
+enum { GIF_GRAPHIC_CONTROL_LABEL = 0xF9 };
+enum { GIF_APPLICATION_EXTENSION_LABEL = 0xFF };
+
+// A GIF decoder's state
+typedef struct gif_struct {
+  // LZW decoder state machine
+  uint8_t* stackp;  // Current stack pointer
+  int datasize;
+  int codesize;
+  int codemask;
+  int avail;  // Index of next available slot in dictionary
+  int oldcode;
+  uint8_t firstchar;
+  int bits;       // Number of unread bits in "datum"
+  int32_t datum;  // 32-bit input buffer
+
+  // Output state machine
+  int64_t pixels_remaining;  // Pixels remaining to be output.
+
+  // Parameters for image frame currently being decoded
+  int tpixel;                // Index of transparent pixel
+  int32_t disposal_method;   // Restore to background, leave in place, etc.
+  uint32_t* local_colormap;  // Per-image colormap
+  uint32_t local_colormap_buffer_size;  // Size of the buffer containing the
+                                        // local colormap.
+  int local_colormap_size;              // Size of local colormap array.
+  uint32_t delay_time;                  // Display time, in milliseconds,
+                                        // for this image in a multi-image GIF
+
+  // Global (multi-image) state
+  int version;           // Either 89 for GIF89 or 87 for GIF87
+  int32_t screen_width;  // Logical screen width & height
+  int32_t screen_height;
+  uint8_t global_colormap_depth;   // Depth of global colormap array
+  uint16_t global_colormap_count;  // Number of colors in global colormap
+  int images_decoded;              // Counts images for multi-part GIFs
+  int loop_count;  // Netscape specific extension block to control
+                   // the number of animation loops a GIF
+                   // renders.
+
+  bool is_transparent;  // TRUE, if tpixel is valid
+
+  uint16_t prefix[MAX_BITS];             // LZW decoding tables
+  uint32_t global_colormap[MAX_COLORS];  // Default colormap if local not
+                                         //   supplied
+  uint8_t suffix[MAX_BITS];              // LZW decoding tables
+  uint8_t stack[MAX_BITS];               // Base of LZW decoder stack
+
+} gif_struct;
+
+#endif  // mozilla_image_decoders_GIF2_H