Roll src/third_party/libwebm/source/ b03c65468..af81f2602 (10 commits)

https://chromium.googlesource.com/webm/libwebm.git/+log/b03c65468b06..af81f26025b7

$ git log b03c65468..af81f2602 --date=short --no-merges --format='%ad %ae %s'
2018-03-02 mjbshaw Fix MSVC warning about 2147483648 not fitting in an int
2018-02-28 mjbshaw Fix compilation with MSVC
2018-02-06 tomfinegan Allow shared builds of libwebm.
2018-01-31 tomfinegan webm2pes: Avoid OOB reads caused by invalid superframe index.
2018-02-01 jzern vp9_header_parser: make SetFrame private
2018-01-30 tomfinegan Limit string element size to 20 million bytes.
2018-01-22 velden Replace uses of deprecated std::auto_ptr with std::unique_ptr.
2018-01-19 mjbshaw Set a maximum limit on element recursion depth
2017-12-18 tomfinegan Silence -Wdeprecated-declarations in GCC 4.7+.
2017-12-07 huisu Update VP9 level definition

Created with:
  roll-dep src/third_party/libwebm/source
BUG=836706

Change-Id: I16a6a0a850e9a47a81176d116af7ddde4fd6c0bf
Reviewed-on: https://chromium-review.googlesource.com/1027561Reviewed-by: Miguel Casas <mcasas@chromium.org>
Commit-Queue: Taiju Tsuiki <tzik@chromium.org>
Cr-Commit-Position: refs/heads/master@{#553897}

DEPS

@@ -745,7 +745,7 @@ deps = {
     Var('chromium_git') + '/webm/libvpx.git' + '@' +  '3b460db214b5bec07a3da6914a224d90c361ccac',
 
   'src/third_party/libwebm/source':
-    Var('chromium_git') + '/webm/libwebm.git' + '@' + 'b03c65468b06d097f27235d93d76bfc45f490ede',
+    Var('chromium_git') + '/webm/libwebm.git' + '@' + 'af81f26025b7435fa9a14ad07c58b44cf9280430',
 
   'src/third_party/libyuv':
     Var('chromium_git') + '/libyuv/libyuv.git' + '@' + 'a9626b9daf62a9b260737e9c2de821ad087b19a1',  # from r1708