In unit tests, StoragePartitionImpl::GetNetworkContext creates NetworkService, but it never gets destroyed.

NetworkService also creates and owns NetworkChangeNotifier, so it gets leaked as well.
NetworkChangeNotifier is supposed to clear g_network_change_notifier in its destructor, but it doesn't happen.
Thus, the next test creating a NetworkChangeNotifier hits "Check failed: !g_network_change_notifier.".

network-service-dev thread - https://groups.google.com/a/chromium.org/forum/#!msg/network-service-dev/IgNFrq1zFHI/FNCAplsCCQAJ