[reliablity] Add crash signature for OnDemuxerBuilt crash.

TBR=willchan@chromium.org
BUG=90577
Review URL: http://codereview.chromium.org/7461091

git-svn-id: svn://svn.chromium.org/chrome/trunk/src/chrome/test/data/reliability@94161 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/known_crashes.txt b/known_crashes.txt
index 6417ded..961e609 100644
--- a/known_crashes.txt
+++ b/known_crashes.txt
@@ -200,3 +200,6 @@
 
 # 90553
 PREFIX: v8::internal::safepointentry::hasregisters___v8::internal::optimizedframe::iterate___v8::internal::isolate::iterate___v8::internal::isolate::iterate
+
+# 90577
+PREFIX: messageloop::calculatedelayedruntime___messageloop::posttask___media::pipelineimpl::ondemuxerbuilt