Fix crash in HungRendererDialogGtk when contents_ == NULL.
Fix crash in HungRendererDialogGtk when contents_ == NULL.

BUG=chromium-os:6004
TEST=none

Review URL: http://codereview.chromium.org/3325010

git-svn-id: http://src.chromium.org/svn/trunk/src@58498 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

Former-commit-id: f7f3236ab1fbfc581ee8116f70963f51f99fa1e4
meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser