update libwebp to v1.2.0

https://chromium.googlesource.com/webm/libwebp/+log/v1.1.0-28-g55a080e5..v1.2.0

- 12/23/2020: version 1.2.0
  * API changes:
    - libwebp:
      encode.h: add a qmin / qmax range for quality factor (cwebp adds -qrange)
  * lossless encoder improvements
  * SIMD support for Wasm builds
  * add xcframeworkbuild.sh, supports Mac Catalyst builds
  * import fuzzers from oss-fuzz & chromium (#409)
  * webpmux: add an '-set loop <value>' option (#494)
  * toolchain updates and bug fixes (#449, #463, #470, #475, #477, #478, #479,
    #488, #491)

Bug: b/170543290
Change-Id: I70f1f053e4e14beefda847f03da006f3acc553a0
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/361896
Commit-Queue: Leon Scroggins <scroggo@google.com>
Reviewed-by: Leon Scroggins <scroggo@google.com>
diff --git a/DEPS b/DEPS
index 8d7c091..cda78b6 100644
--- a/DEPS
+++ b/DEPS
@@ -27,7 +27,7 @@
   "third_party/externals/libgifcodec"     : "https://skia.googlesource.com/libgifcodec@fd59fa92a0c86788dcdd84d091e1ce81eda06a77",
   "third_party/externals/libjpeg-turbo"   : "https://chromium.googlesource.com/chromium/deps/libjpeg_turbo.git@64fc43d52351ed52143208ce6a656c03db56462b",
   "third_party/externals/libpng"          : "https://skia.googlesource.com/third_party/libpng.git@386707c6d19b974ca2e3db7f5c61873813c6fe44",
-  "third_party/externals/libwebp"         : "https://chromium.googlesource.com/webm/libwebp.git@55a080e50af655d1fbe0a5c22954835cdd59ff92",
+  "third_party/externals/libwebp"         : "https://chromium.googlesource.com/webm/libwebp.git@fedac6cc69cda3e9e04b780d324cf03921fb3ff4",
   "third_party/externals/lua"             : "https://skia.googlesource.com/external/github.com/lua/lua.git@e354c6355e7f48e087678ec49e340ca0696725b1",
   "third_party/externals/microhttpd"      : "https://android.googlesource.com/platform/external/libmicrohttpd@748945ec6f1c67b7efc934ab0808e1d32f2fb98d",
   "third_party/externals/oboe"            : "https://chromium.googlesource.com/external/github.com/google/oboe.git@b02a12d1dd821118763debec6b83d00a8a0ee419",