Fixed the memory leak of callback Task in PostPingMessage. If PostTask to watched thread fails, we will stop monitoring that thread.
Fixed the memory leak of callback Task in PostPingMessage.
If PostTask to watched thread fails, we will stop monitoring
that thread.

BUG=73915,73844
TEST=performance testing

Review URL: http://codereview.chromium.org/6575007

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@75838 0039d316-1c4b-4281-b951-d872f2087c98

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