Add error handling to validate expectation names.

Do not allow slashes (\ or /), quotes (" or ') or spaces.

BUG=None
NOTRY=True

Review URL: https://codereview.chromium.org/100623002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@238443 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 238443