NetworkStatsService to adjust VPN stats before recording.

* Creates a new Parcelable class VpnInfo to hold required
  parameters for VPN stats adjustments.
* ConnectivityService to collect infomation and provide
  a list of VpnInfo, one for each user.
* NetworkStatsService passes the VpnInfo array to
  NetworkStatsRecorder.
* NetworkStatsRecorder calls NetworkStats.migrateTun()
  to do the math.
* Poll NetworkStats when the vpn application calls
  setUnderlyingNetworks().

Bug: 19536273
Change-Id: I7a4c7726b8243fead10416f7ec6eb5cf95f20183

core/java/com/android/internal/net/VpnInfo.aidl

@@ -0,0 +1,19 @@
+/*
+ * Copyright (C) 2015 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.internal.net;
+
+parcelable VpnInfo;