PermissionUtil::GetPermissionType needs to handle MIDI

After the recent PermissionManager's change, it calls
GetPermissionType even for CONTENT_SETTING_TYPE_MIDI.

BUG=697771

Review-Url: https://codereview.chromium.org/2730693002
Cr-Commit-Position: refs/heads/master@{#454231}
bool PermissionUtil::ShouldShowPersistenceToggle() {
  return base::FeatureList::IsEnabled(
      features::kDisplayPersistenceToggleInPermissionPrompts);
}

bool PermissionUtil::ShouldShowPersistenceToggle() {
  return base::FeatureList::IsEnabled(
      features::kDisplayPersistenceToggleInPermissionPrompts);
}
