Add support for multiple frames in SkCodec

BUILD.gn

 # Copyright 2016 Google Inc.
 #
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("gn/shared_sources.gni")
 
 if (!defined(is_skia_standalone)) {
   is_skia_standalone = false
 }
 
 declare_args() {
   skia_use_angle = false
   skia_use_expat = true
   skia_use_fontconfig = is_linux
   skia_use_freetype = is_android || is_fuchsia || is_linux
-  skia_use_giflib = !is_fuchsia
+  skia_use_giflib = true
   skia_use_libjpeg_turbo = true
   skia_use_libpng = true
   skia_use_libwebp = !is_fuchsia
   skia_use_mesa = false
   skia_use_sfntly = !is_fuchsia && !is_win  # TODO: icu on Windows, re-enable this.
   skia_use_vulkan = is_android && defined(ndk_api) && ndk_api >= 24
   skia_use_zlib = true
 
   skia_enable_android_framework_defines = false
   skia_enable_gpu = true
@@ skipping 305 matching lines @@
     "//third_party/freetype2",
   ]
   sources = [
     "src/ports/SkFontMgr_custom.cpp",
     "src/ports/SkFontMgr_custom_empty_factory.cpp",
   ]
 }
 
 optional("gif") {
   enabled = skia_use_giflib
   public_defines = [ "SK_HAS_GIF_LIBRARY" ]

[msarett, 2016/10/18 20:04:36]

Now that we don't depend on giflib, can we get rid of this define and just
always compile SkGifCodec?

Might need to grep for SK_HAS_GIF_LIBRARY and delete it from a bunch of build
files...

[scroggo_chromium, 2016/10/18 20:41:47]

Done.

 
-  deps = [
-    "//third_party/giflib",
-  ]
   sources = [
+    "src/codec/GIFImageReader.cpp",
     "src/codec/SkGifCodec.cpp",
   ]
 }
 
 optional("gpu") {
   enabled = skia_enable_gpu
   public_defines = []
 
   sources = skia_gpu_sources + [ "src/gpu/gl/GrGLDefaultInterface_native.cpp" ]
 
@@ skipping 684 matching lines @@
       "tools/DumpRecord.cpp",
       "tools/dump_record.cpp",
     ]
     deps = [
       ":flags",
       ":skia",
     ]
     testonly = true
   }
 }