Add support for multiple frames in SkCodec

BUILD.gn

Index: BUILD.gn
diff --git a/BUILD.gn b/BUILD.gn
index 3f88df5d279f4c6473054c6007bde952c14513f6..189d34a59e921ec33038a086d66fc0b49c9414ae 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -14,7 +14,7 @@ declare_args() {
   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
@@ -342,11 +342,9 @@ optional("gif") {
   enabled = skia_use_giflib
   public_defines = [ "SK_HAS_GIF_LIBRARY" ]
 
-  deps = [
-    "//third_party/giflib",
-  ]
   sources = [
     "src/codec/SkGifCodec.cpp",
+    "src/codec/GIFImageReader.cpp",

[scroggo_chromium, 2016/10/17 20:53:56]

I've clearly done something wrong here. When I upload, I get the following
message:

`gn format --dry-run BUILD.gn` failed, try
	gn format BUILD.gn

When I try to run that, I get:

scroggo@scroggo-linux4:/usr/local/google/skia$ gn format BUILD.gn 
gn.py: Could not find gn executable at:
/usr/local/google/skia/./buildtools/linux64/gn

Will fix before submitting...

[scroggo_chromium, 2016/10/17 21:16:19]

Fixed.

   ]
 }