Address comments about safely casting handles.
Address comments about safely casting handles.

The debug version exactly follows the original code. Release mode
avoid creating a temporary handle.
Review URL: https://codereview.chromium.org//11500004

git-svn-id: c93d8a2297af3b929165606efe145742a534bc71@17703 260f80e4-7a28-3924-810f-c04153c831b5

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