Workaround for Pango integer overflow on really long strings.
Workaround for Pango integer overflow on really long strings.

This fixes TextEliderTest.ElideTextLongStrings breakage on "Linux Tests (dbg-shlib)(1)" (Karmic).
http://chrome-buildbot.corp.google.com:8016/builders/Linux%20Tests%20(dbg-shlib)(1)/builds/1367/steps/app_unittests/logs/stdio

Review URL: http://codereview.chromium.org/661244

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@40297 0039d316-1c4b-4281-b951-d872f2087c98

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