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It makes more sense to try to open the entries first rather than create them, since they will usually only not exist the first time.

Review URL: https://codereview.chromium.org/465633003

Cr-Commit-Position: refs/heads/master@{#289342}
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@289342 0039d316-1c4b-4281-b951-d872f2087c98