BUG=50006 (and various other reports)
TEST=Run chrome under nested window manager using Xephyr (see
http://code.google.com/p/chromium/wiki/LayoutTestsLinux)

use --enable-logging=stderr --log-level=0
kill xephyr
examine log. You should see
X IO Error detected
followed (not necessarily immediately) by
successfully saved /tmp/tx/Default/Preferences
successfully saved /tmp/tx/Local State
successfully saved /tmp/tx/Local State
successfully saved /tmp/tx/Default/Preferences
along with no crash.

There is a high ranking crash report on both linux and chromeos that happens whenever X sends an error to chrome. This change causes us to log and continue when we get a regular error from X. When we get an IO error, indicating X is gone, we attempt to shut down gracefully.

Review URL: http://codereview.chromium.org/3175038

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@59147 0039d316-1c4b-4281-b951-d872f2087c98