Roll chromium_revision c2239a8..4e76e79 (334133:334321)

Relevant changes:
* src/third_party/libvpx: a436311..db3f347
Details: https://chromium.googlesource.com/chromium/src/+/c2239a8..4e76e79/DEPS

Clang version was not updated in this roll.

BUG=
R=pbos@webrtc.org

Review URL: https://codereview.webrtc.org/1176243005.

Cr-Commit-Position: refs/heads/master@{#9437}
diff --git a/DEPS b/DEPS
index 621d577..b2c873c 100644
--- a/DEPS
+++ b/DEPS
@@ -6,7 +6,7 @@
 vars = {
   'extra_gyp_flag': '-Dextra_gyp_flag=0',
   'chromium_git': 'https://chromium.googlesource.com',
-  'chromium_revision': 'c2239a84ca03a01bb95d6055d2a6c75b767979fb',
+  'chromium_revision': '4e76e7926ee51bdfdd635437920f455ae6444912',
 }
 
 # NOTE: Prefer revision numbers to tags for svn deps. Use http rather than