Added trace on Data Saver-related methods.

BUG: 31389946
Test: m -j32 cts && cts-tradefed run commandAndExit cts -m CtsHostsideNetworkTests -t com.android.cts.net.HostsideRestrictBackgroundNetworkTests

Change-Id: I4a4299371a529121438db166fe03de8263812323
diff --git a/services/core/java/com/android/server/NetworkManagementService.java b/services/core/java/com/android/server/NetworkManagementService.java
index 8f16504..e64aa16 100644
--- a/services/core/java/com/android/server/NetworkManagementService.java
+++ b/services/core/java/com/android/server/NetworkManagementService.java
@@ -77,6 +77,7 @@
 import android.os.StrictMode;
 import android.os.SystemClock;
 import android.os.SystemProperties;
+import android.os.Trace;
 import android.provider.Settings;
 import android.telephony.DataConnectionRealTimeInfo;
 import android.telephony.PhoneStateListener;
@@ -1699,6 +1700,7 @@
                 return;
             }
 
+            Trace.traceBegin(Trace.TRACE_TAG_NETWORK, "inetd bandwidth");
             try {
                 mConnector.execute("bandwidth", suffix + chain, uid);
                 if (enable) {
@@ -1708,6 +1710,8 @@
                 }
             } catch (NativeDaemonConnectorException e) {
                 throw e.rethrowAsParcelableException();
+            } finally {
+                Trace.traceEnd(Trace.TRACE_TAG_NETWORK);
             }
         }
     }
@@ -1730,6 +1734,7 @@
                 Log.w(TAG, "setDataSaverMode(): already " + mDataSaverMode);
                 return true;
             }
+            Trace.traceBegin(Trace.TRACE_TAG_NETWORK, "bandwidthEnableDataSaver");
             try {
                 final boolean changed = mNetdService.bandwidthEnableDataSaver(enable);
                 if (changed) {
@@ -1741,6 +1746,8 @@
             } catch (RemoteException e) {
                 Log.w(TAG, "setDataSaverMode(" + enable + "): netd command failed", e);
                 return false;
+            } finally {
+                Trace.traceEnd(Trace.TRACE_TAG_NETWORK);
             }
         }
     }