Add support for multiple frames in SkCodec

BUILD.gn

Index: BUILD.gn
diff --git a/BUILD.gn b/BUILD.gn
index 25985e1019724e1e41d76a96316f14bd140163a1..c1863e1d9468e5685afc442892c0daaccdcd64d9 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -15,7 +15,6 @@ declare_args() {
   skia_use_fontconfig = is_linux
   skia_use_freetype = is_android || is_fuchsia || is_linux
   skia_use_gdi = false
-  skia_use_giflib = !is_fuchsia
   skia_use_libjpeg_turbo = true
   skia_use_libpng = true
   skia_use_libwebp = !is_fuchsia
@@ -348,18 +347,6 @@ optional("fontmgr_fuchsia") {
   ]
 }
 
-optional("gif") {
-  enabled = skia_use_giflib
-  public_defines = [ "SK_HAS_GIF_LIBRARY" ]
-
-  deps = [
-    "//third_party/giflib",
-  ]
-  sources = [
-    "src/codec/SkGifCodec.cpp",
-  ]
-}
-
 optional("gpu") {
   enabled = skia_enable_gpu
   public_defines = []
@@ -493,7 +480,6 @@ component("skia") {
     ":fontmgr_custom",
     ":fontmgr_fontconfig",
     ":fontmgr_fuchsia",
-    ":gif",
     ":gpu",
     ":hsw",
     ":jpeg",
@@ -517,6 +503,7 @@ component("skia") {
   sources += [
     "src/android/SkBitmapRegionCodec.cpp",
     "src/android/SkBitmapRegionDecoder.cpp",
+    "src/codec/GIFImageReader.cpp",
     "src/codec/SkAndroidCodec.cpp",
     "src/codec/SkBmpCodec.cpp",
     "src/codec/SkBmpMaskCodec.cpp",
@@ -524,10 +511,12 @@ component("skia") {
     "src/codec/SkBmpStandardCodec.cpp",
     "src/codec/SkCodec.cpp",
     "src/codec/SkCodecImageGenerator.cpp",
+    "src/codec/SkGifCodec.cpp",
     "src/codec/SkMaskSwizzler.cpp",
     "src/codec/SkMasks.cpp",
     "src/codec/SkSampledCodec.cpp",
     "src/codec/SkSampler.cpp",
+    "src/codec/SkStreamBuffer.cpp",
     "src/codec/SkSwizzler.cpp",
     "src/codec/SkWbmpCodec.cpp",
     "src/images/SkImageEncoder.cpp",
@@ -819,6 +808,7 @@ if (skia_enable_tools) {
     public_include_dirs = [ "gm" ]
     sources = gm_sources
     deps = [
+      ":flags",
       ":gpu_tool_utils",
       ":skia",
       ":tool_utils",