Flip enable_skia_wuffs_gif gn arg default to false

This undoes crrev.com/c/1898151 "Flip enable_skia_wuffs_gif gn arg
default to true", as there have been reports (crbug.com/1023129,
crbug.com/1023191) of ARM performance regressions, and fixing those is
ongoing work. We might try flipping the default back to true after the
upcoming M80 branch point.

Also fix build of skia when enable_skia_wuffs_gif=false.

The libgifcodec dependency isn't really new. It was spun out of the
existing Skia git repository a couple of weeks ago:
    https://review.skia.org/255780

Fix to: https://crrev.com/c/1942595

Bug: 1014044
Bug: 1023129
Bug: 1023191
Change-Id: Icfd7e9b703cb1c7d25f891937d54a01f97711389
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1944286
Commit-Queue: Hal Canary <halcanary@google.com>
Reviewed-by: Nigel Tao <nigeltao@chromium.org>
Reviewed-by: Leon Scroggins <scroggo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#721190}

DEPS

@@ -320,6 +320,10 @@ vars = {
   # the commit queue can handle CLs rolling wuffs
   # and whatever else without interference from each other.
   'wuffs_revision': '7ec252876541ec203659949450fafddc148b606e',
+  # Three lines of non-changing comments so that
+  # the commit queue can handle CLs rolling libgifcodec
+  # and whatever else without interference from each other.
+  'libgifcodec_revision': '3815a0321b8e99a9eb35309c80334a43c2c49ff2',
 
   # TODO(crbug.com/941824): The values below need to be kept in sync
   # between //DEPS and //buildtools/DEPS, so if you're updating one,
@@ -1496,6 +1500,9 @@ deps = {
   'src/third_party/webrtc':
     Var('webrtc_git') + '/src.git' + '@' + '89313451d8e2338845716b0ab8760ed0552580f9',
 
+  'src/third_party/libgifcodec':
+     Var('skia_git') + '/libgifcodec' + '@'+  Var('libgifcodec_revision'),
+
   # Wuffs' canonical repository is at github.com/google/wuffs, but we use
   # Skia's mirror of Wuffs, the same as in upstream Skia's DEPS file.
   'src/third_party/wuffs/src':

skia/BUILD.gn

@@ -10,6 +10,7 @@ import("//build/config/sanitizers/sanitizers.gni")
 import("//gpu/vulkan/features.gni")
 import("//printing/buildflags/buildflags.gni")
 import("//testing/test.gni")
+import("//third_party/libgifcodec/libgifcodec.gni")
 import("//third_party/skia/gn/shared_sources.gni")
 import("//third_party/skia/third_party/skcms/skcms.gni")
 import("features.gni")
@@ -26,7 +27,7 @@ skia_support_pdf = !is_ios && enable_basic_printing
 skia_support_skottie = true
 
 declare_args() {
-  enable_skia_wuffs_gif = true
+  enable_skia_wuffs_gif = false
   skia_whitelist_serialized_typefaces = false
 }
 
@@ -43,6 +44,8 @@ config("skia_config") {
   if (!is_ios) {
     if (enable_skia_wuffs_gif) {
       include_dirs += [ "//third_party/wuffs/src/release/c" ]
+    } else {
+      include_dirs += [ "//third_party/libgifcodec" ]
     }
   }
   if (enable_vulkan) {
@@ -67,6 +70,8 @@ config("skia_config") {
     defines += [ "SK_HAS_JPEG_LIBRARY" ]
     if (enable_skia_wuffs_gif) {
       defines += [ "SK_HAS_WUFFS_LIBRARY" ]
+    } else {
+      defines += [ "SK_USE_LIBGIFCODEC" ]
     }
   }
   if (enable_vulkan) {
@@ -358,10 +363,9 @@ component("skia") {
       deps += [ "//third_party/wuffs" ]
       sources += [ "//third_party/skia/src/codec/SkWuffsCodec.cpp" ]
     } else {
-      sources += [
-        "//third_party/skia/src/codec/SkGifCodec.cpp",
-        "//third_party/skia/third_party/gif/SkGifImageReader.cpp",
-      ]
+      sources += rebase_path(libgifcodec_sources + libgifcodec_public,
+                             ".",
+                             "//third_party/libgifcodec")
     }
   }