Check the content setting type is valid.

BUG=169770
Review URL: https://codereview.chromium.org/11875013

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@176687 0039d316-1c4b-4281-b951-d872f2087c98
TabSpecificContentSettings::SiteDataObserver::SiteDataObserver(
    TabSpecificContentSettings* tab_specific_content_settings)
    : tab_specific_content_settings_(tab_specific_content_settings) {
  tab_specific_content_settings_->AddSiteDataObserver(this);
}

TabSpecificContentSettings::SiteDataObserver::SiteDataObserver(
    TabSpecificContentSettings* tab_specific_content_settings)
    : tab_specific_content_settings_(tab_specific_content_settings) {
  tab_specific_content_settings_->AddSiteDataObserver(this);
}
