Cleanup: DeleteTask() no longer exists. Update BrowserThread comments and remove reliability suppression.

BUG=21054
TEST=none
Review URL: https://chromiumcodereview.appspot.com/10598003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src/chrome/test/data/reliability@143310 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/known_crashes.txt b/known_crashes.txt
index f7ca518..55dba8b 100644
--- a/known_crashes.txt
+++ b/known_crashes.txt
@@ -156,9 +156,6 @@
 # 77176
 PREFIX: webcore::implicitanimation::~implicitanimation___webcore::implicitanimation::`scalar deleting destructor'___wtf::hashtable<wtf::refptr<webcore::animationbase>,wtf::refptr<webcore::animationbase>,wtf::identityextractor<wtf::refptr<webcore::animationbase> >,wtf::ptrhash<wtf::refptr<webcore::animationbase> >,wtf::hashtraits<wtf::refptr<webcore::animationbase> >,wtf::hashtraits<wtf::refptr<webcore::animationbase> > >::deallocatetable
 
-# 21054
-REGEX : ^deletetask.*::run___messageloop::runtask___messageloop::dowork
-
 # 84178
 PREFIX: `anonymous namespace'::establishchannelcallback::send___`anonymous namespace'::establishchannelcallback::runwithparams___gpuprocesshost::sendoutstandingreplies