Don't allow extensions to take screenshots of interstitial pages. Branched from
https://codereview.chromium.org/14885004/ which is trying to test it.

BUG=229504

Review URL: https://chromiumcodereview.appspot.com/14954004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@198297 0039d316-1c4b-4281-b951-d872f2087c98
QueryArg ParseBoolQueryArg(base::DictionaryValue* query, const char* key) {
  if (query->HasKey(key)) {
    bool value = false;
    CHECK(query->GetBoolean(key, &value));
    return value ? MATCH_TRUE : MATCH_FALSE;
  }
  return NOT_SET;
}

QueryArg ParseBoolQueryArg(base::DictionaryValue* query, const char* key) {
  if (query->HasKey(key)) {
    bool value = false;
    CHECK(query->GetBoolean(key, &value));
    return value ? MATCH_TRUE : MATCH_FALSE;
  }
  return NOT_SET;
}
