Http cache: Remove a race between the http cache destructor deleting the pending operations, and the disk cache using data backed by the pending operation.
Http cache: Remove a race between the http cache destructor
deleting the pending operations, and the disk cache using data
backed by the pending operation.

BUG=87396
TEST=none
Review URL: http://codereview.chromium.org/7277009

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@90802 0039d316-1c4b-4281-b951-d872f2087c98

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