[Mac] Ignore spell-checker exceptions.
Pasteboard corruption or bad third-party code can cause
+[NSSpellChecker sharedSpellChecker] to throw NSExceptions. Chrome
treats NSExceptions as fatal, because they generally mean things are
awry. Since this call can happen in response to calls from the
renderer, and the exceptions are not thrown from Chrome code, this
change enables them while retrieving the shared instance.
BUG=92399,95728
Review URL: http://codereview.chromium.org/
8883040
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@113891 0039d316-1c4b-4281-b951-d872f2087c98