Add the defaultNetwork element to the netstats.proto.

This is in its own commit because AOSP has diverged from internal
master.

Bug: 35142602
Test: builds, boots
Change-Id: I75fc85b961bc919e3d6c2adce6d6861c6f2c8379
Merged-In: I75fc85b961bc919e3d6c2adce6d6861c6f2c8379

core/java/android/net/NetworkIdentity.java

@@ -130,6 +130,7 @@ public class NetworkIdentity implements Comparable<NetworkIdentity> {
         proto.write(NetworkIdentityProto.NETWORK_ID, mNetworkId);
         proto.write(NetworkIdentityProto.ROAMING, mRoaming);
         proto.write(NetworkIdentityProto.METERED, mMetered);
+        proto.write(NetworkIdentityProto.DEFAULT_NETWORK, mDefaultNetwork);
 
         proto.end(start);
     }

core/proto/android/service/netstats.proto

@@ -64,6 +64,8 @@ message NetworkIdentityProto {
     bool roaming = 4;
 
     bool metered = 5;
+
+    bool default_network = 6;
 }
 
 // Corresponds to NetworkStatsRecorder.