GTK: remove superflous focus grabbing calls that cause crashes in debug mode.
GTK: remove superflous focus grabbing calls that cause crashes in debug mode.

The body of OnPromptShown handles default focus.

BUG=none
TEST=middle click on a link that requires http auth in debug mode, the browser shouldn't crash

Review URL: http://codereview.chromium.org/554042

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@36817 0039d316-1c4b-4281-b951-d872f2087c98

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