Support monitoring tethered interface

This would be useful to be used in together with Instant Tethering + Turn off hotspot automatically.

Refine #26, #53.

mobile/src/main/res/drawable/ic_image_remove_red_eye.xml

@@ -0,0 +1,10 @@
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+        android:width="24dp"
+        android:height="24dp"
+        android:viewportWidth="24.0"
+        android:viewportHeight="24.0"
+        android:tint="?attr/colorControlNormal">
+    <path
+        android:fillColor="#FF000000"
+        android:pathData="M12,4.5C7,4.5 2.73,7.61 1,12c1.73,4.39 6,7.5 11,7.5s9.27,-3.11 11,-7.5c-1.73,-4.39 -6,-7.5 -11,-7.5zM12,17c-2.76,0 -5,-2.24 -5,-5s2.24,-5 5,-5 5,2.24 5,5 -2.24,5 -5,5zM12,9c-1.66,0 -3,1.34 -3,3s1.34,3 3,3 3,-1.34 3,-3 -1.34,-3 -3,-3z"/>
+</vector>

mobile/src/main/res/menu/toolbar_monitor.xml

@@ -0,0 +1,10 @@
+<?xml version="1.0" encoding="utf-8"?>
+<menu xmlns:android="http://schemas.android.com/apk/res/android"
+      xmlns:app="http://schemas.android.com/apk/res-auto">
+    <item android:id="@+id/monitor"
+          android:icon="@drawable/ic_image_remove_red_eye"
+          android:title="@string/tethering_monitor"
+          app:showAsAction="always">
+        <menu/>
+    </item>
+</menu>

mobile/src/main/res/values-zh-rCN/strings.xml

@@ -39,6 +39,9 @@
     <string name="tethering_temp_hotspot_failure_incompatible_mode">模式不兼容</string>
     <string name="tethering_temp_hotspot_failure_tethering_disallowed">共享被禁用</string>
 
+    <string name="tethering_monitor">监视…</string>
+    <string name="tethering_state_monitored">%s（监视）</string>
+
     <string name="tethering_manage">管理系统共享…</string>
     <string name="tethering_manage_offload_enabled">若 VPN 共享无法使用，请尝试禁用“开发者选项”中的“网络共享硬件加速”。</string>
     <!--
@@ -122,6 +125,7 @@
     <plurals name="notification_interfaces">
         <item quantity="other">%d 个接口</item>
     </plurals>
+    <string name="notification_interfaces_inactive">不活跃：</string>
 
     <string name="failure_reason_unknown">未知 #%d</string>
     <string name="exception_interface_not_found">错误：未找到下游接口</string>

mobile/src/main/res/values/strings.xml

@@ -49,6 +49,9 @@
     <string name="tethering_temp_hotspot_failure_incompatible_mode">incompatible mode</string>
     <string name="tethering_temp_hotspot_failure_tethering_disallowed">tethering disallowed</string>
 
+    <string name="tethering_monitor">Monitor…</string>
+    <string name="tethering_state_monitored">%s (monitored)</string>
+
     <string name="tethering_manage">Manage system tethering…</string>
     <string name="tethering_manage_offload_enabled">Please disable Tethering hardware acceleration in Developer options
         if VPN tethering does not work.</string>
@@ -131,6 +134,7 @@
         <item quantity="one">%d interface</item>
         <item quantity="other">%d interfaces</item>
     </plurals>
+    <string name="notification_interfaces_inactive">"Inactive: "</string>
 
     <string name="failure_reason_unknown">unknown #%d</string>
     <string name="exception_interface_not_found">Fatal: Downstream interface not found</string>