libwebp: update to v0.5.1

third_party/libwebp/README.chromium

Index: third_party/libwebp/README.chromium
diff --git a/third_party/libwebp/README.chromium b/third_party/libwebp/README.chromium
index 699b28d40504d380990046f8a38d300cf7353662..4c697457098ae00c4a852b8c8a151877a94c516e 100644
--- a/third_party/libwebp/README.chromium
+++ b/third_party/libwebp/README.chromium
@@ -1,14 +1,14 @@
 Name: WebP image encoder/decoder
 Short Name: libwebp
 URL: http://developers.google.com/speed/webp
-Version: v0.5.0
+Version: v0.5.1
 License: BSD
 License File: LICENSE
 Security Critical: Yes
 
 Description:
 Source archive:
-  http://downloads.webmproject.org/releases/webp/libwebp-0.5.0.tar.gz
+  http://downloads.webmproject.org/releases/webp/libwebp-0.5.1.tar.gz
 
 WebP is an image format that does both lossy and lossless compression of
 digital photographic images. WebP consists of a codec based on VP8, that Google
@@ -20,7 +20,6 @@ Local changes:
  * Removed examples/, documentation and build related files, keeping only
    the contents of src/ less mux/ which is unused.
  * Merged COPYING/PATENTS to LICENSE
- * Added an explicit cast to short in yuv_sse2.c
  * Disabled "-frename-registers" flag for ARM64 linux build as clang(3.9.0)
    build fails with error - unsupported flag.
 Cherry-picks: