Allow testing of signal strength

- Let any process with NETWORK_SETTINGS register for signal strength
  wakeup.
- Allow agents registering test networks to assign them a signal
  strength.

Test: NetworkAgentTest
Bug: 139268426
Change-Id: Iebfeb9316bcbd8472459c517abb16f1f9d879871
Merged-In: I2b4b89be3e69f4853fd6978d2c8f5c8eb4271f21
(cherry picked from commit 5cc7b18fe7fa94ce2e30572c476df445ed337741, aosp/1284585)
diff --git a/core/java/android/net/NetworkCapabilities.java b/core/java/android/net/NetworkCapabilities.java
index 73c6b3d..52d6fdf 100644
--- a/core/java/android/net/NetworkCapabilities.java
+++ b/core/java/android/net/NetworkCapabilities.java
@@ -680,11 +680,13 @@
     public void restrictCapabilitesForTestNetwork() {
         final long originalCapabilities = mNetworkCapabilities;
         final NetworkSpecifier originalSpecifier = mNetworkSpecifier;
+        final int originalSignalStrength = mSignalStrength;
         clearAll();
         // Reset the transports to only contain TRANSPORT_TEST.
         mTransportTypes = (1 << TRANSPORT_TEST);
         mNetworkCapabilities = originalCapabilities & TEST_NETWORKS_ALLOWED_CAPABILITIES;
         mNetworkSpecifier = originalSpecifier;
+        mSignalStrength = originalSignalStrength;
     }
 
     /**