Extend network stats to signatureOrSystem.

    <permission android:name="android.permission.READ_NETWORK_USAGE_HISTORY"

        android:label="@string/permlab_readNetworkUsageHistory"

        android:description="@string/permdesc_readNetworkUsageHistory"

        android:protectionLevel="signature" />

        android:protectionLevel="signatureOrSystem" />

    <!-- Allows an application to manage network policies (such as warning and disable

         limits) and to define application-specific rules. @hide -->