Created new public API so applications can customize its metered network
usage while running in background.

The new API is 'int getRestrictBackgroundStatus()' and returns the
following values:

 - RESTRICT_BACKGROUND_STATUS_DISABLED: no restrictions
 - RESTRICT_BACKGROUND_STATUS_WHITELISTED: restriction but app is
   whitelisted
 - RESTRICT_BACKGROUND_STATUS_ENABLED: full restriction

The proper way to interprete these values for using metered networks
while running on background is:

 - When disabled, there is no restriction and the application could use the
   metered networks freely.

 - When whitelisted, the application can use the metered network, but should try
   to minimize the usage.

 - When enabled, the application should not try to use metered networks at
   all, since the usage will be denied.

BUG: 26451391
Change-Id: If07d42bb88e4c02802df0234861f38aef2cfead7
diff --git a/core/java/android/net/ConnectivityManager.java b/core/java/android/net/ConnectivityManager.java
index c4f0847..5584cde 100644
--- a/core/java/android/net/ConnectivityManager.java
+++ b/core/java/android/net/ConnectivityManager.java
@@ -16,7 +16,7 @@
 package android.net;
 
 import static com.android.internal.util.Preconditions.checkNotNull;
-
+import android.annotation.IntDef;
 import android.annotation.Nullable;
 import android.annotation.SdkConstant;
 import android.annotation.SdkConstant.SdkConstantType;
@@ -49,6 +49,8 @@
 
 import libcore.net.event.NetworkEventDispatcher;
 
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
 import java.net.InetAddress;
 import java.util.HashMap;
 import java.util.concurrent.atomic.AtomicInteger;
@@ -512,6 +514,7 @@
     private final Context mContext;
 
     private INetworkManagementService mNMService;
+    private INetworkPolicyManager mNPManager;
 
     /**
      * Tests if a given integer represents a valid network type.
@@ -3025,4 +3028,58 @@
         return NetworkUtils.bindProcessToNetworkForHostResolution(
                 network == null ? NETID_UNSET : network.netId);
     }
+
+    /**
+     * Device is not restricting metered network activity while application is running on
+     * background.
+     */
+    public static final int RESTRICT_BACKGROUND_STATUS_DISABLED = 1;
+
+    /**
+     * Device is restricting metered network activity while application is running on background,
+     * but application is allowed to bypass it.
+     * <p>
+     * In this state, application should take action to mitigate metered network access.
+     * For example, a music streaming application should switch to a low-bandwidth bitrate.
+     */
+    public static final int RESTRICT_BACKGROUND_STATUS_WHITELISTED = 2;
+
+    /**
+     * Device is restricting metered network activity while application is running on background.
+     * In this state, application should not try to use the network while running on background,
+     * because it would be denied.
+     */
+    public static final int RESTRICT_BACKGROUND_STATUS_ENABLED = 3;
+
+    @IntDef(flag = false, value = {
+            RESTRICT_BACKGROUND_STATUS_DISABLED,
+            RESTRICT_BACKGROUND_STATUS_WHITELISTED,
+            RESTRICT_BACKGROUND_STATUS_ENABLED,
+    })
+    @Retention(RetentionPolicy.SOURCE)
+    public @interface RestrictBackgroundStatus {
+    }
+
+    private INetworkPolicyManager getNetworkPolicyManager() {
+        synchronized (this) {
+            if (mNPManager != null) {
+                return mNPManager;
+            }
+            mNPManager = INetworkPolicyManager.Stub.asInterface(ServiceManager
+                    .getService(Context.NETWORK_POLICY_SERVICE));
+            return mNPManager;
+        }
+    }
+
+    /**
+     * Determines if the calling application is subject to metered network restrictions while
+     * running on background.
+     */
+    public @RestrictBackgroundStatus int getRestrictBackgroundStatus() {
+        try {
+            return getNetworkPolicyManager().getRestrictBackgroundByCaller();
+        } catch (RemoteException e) {
+            return RESTRICT_BACKGROUND_STATUS_DISABLED;
+        }
+    }
 }