Disable crash reporting in Guest mode.
Disable crash reporting in Guest mode.

BUG=chromium-os:7203
TEST=Check that crash reporting is not enabled when in Guest mode. Try to crash browser, e.g. by going to about:crash

Review URL: http://codereview.chromium.org/4350003

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@87453 0039d316-1c4b-4281-b951-d872f2087c98

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