update libwebp to v1.2.0
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 <995cad867ca30d6399abe011583a53547c8afea1@google.com>
Reviewed-by: Leon Scroggins <995cad867ca30d6399abe011583a53547c8afea1@google.com>

aosp-mirror/platform_external_skia,google/skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,google/skia,aosp-mirror/platform_external_skia,google/skia,google/skia,aosp-mirror/platform_external_skia,google/skia,google/skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,google/skia,google/skia,aosp-mirror/platform_external_skia,google/skia,aosp-mirror/platform_external_skia,google/skia