Dynamically register the power broadcast receiver.

base/android/java/src/org/chromium/base/PowerMonitor.java

 // Copyright 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 package org.chromium.base;
 
+import android.content.BroadcastReceiver;
 import android.content.Context;
 import android.content.Intent;
 import android.content.IntentFilter;
 import android.os.BatteryManager;
 import android.os.Handler;
 import android.os.Looper;
 
 import org.chromium.base.annotations.CalledByNative;
 import org.chromium.base.annotations.JNINamespace;
 
-
 /**
  * Integrates native PowerMonitor with the java side.
  */
 @JNINamespace("base::android")
 public class PowerMonitor  {
     private static class LazyHolder {
         private static final PowerMonitor INSTANCE = new PowerMonitor();
     }
     private static PowerMonitor sInstance;
 
     private boolean mIsBatteryPower;
     private final Handler mHandler = new Handler(Looper.getMainLooper());
 
-    public static void createForTests(Context context) {
+    public static void createForTests() {
         // Applications will create this once the JNI side has been fully wired up both sides. For
         // tests, we just need native -> java, that is, we don't need to notify java -> native on
         // creation.
         sInstance = LazyHolder.INSTANCE;
     }
 
     /**
      * Create a PowerMonitor instance if none exists.
-     * @param context The context to register broadcast receivers for.  The application context
-     *                will be used from this parameter.
      */
-    public static void create(Context context) {
-        context = context.getApplicationContext();
-        if (sInstance == null) {
-            sInstance = LazyHolder.INSTANCE;
-            IntentFilter ifilter = new IntentFilter(Intent.ACTION_BATTERY_CHANGED);
-            Intent batteryStatusIntent = context.registerReceiver(null, ifilter);
-            if (batteryStatusIntent != null) onBatteryChargingChanged(batteryStatusIntent);
-        }
+    public static void create() {
+        if (sInstance != null) return;

[nyquist, 2017/01/23 22:42:01]

Since this is a public method, should we assert anything about which thread this
runs on? Maybe just assert main thread or something like that?

[Ted C, 2017/01/23 22:49:34]

Done.

+
+        Context context = ContextUtils.getApplicationContext();
+        sInstance = LazyHolder.INSTANCE;
+        IntentFilter ifilter = new IntentFilter(Intent.ACTION_BATTERY_CHANGED);
+        Intent batteryStatusIntent = context.registerReceiver(null, ifilter);
+        if (batteryStatusIntent != null) onBatteryChargingChanged(batteryStatusIntent);
+
+        IntentFilter powerConnectedFilter = new IntentFilter();
+        powerConnectedFilter.addAction(Intent.ACTION_POWER_CONNECTED);
+        powerConnectedFilter.addAction(Intent.ACTION_POWER_DISCONNECTED);
+        context.registerReceiver(new BroadcastReceiver() {
+            @Override
+            public void onReceive(Context context, Intent intent) {
+                PowerMonitor.onBatteryChargingChanged(intent);
+            }
+        }, powerConnectedFilter);
     }
 
     private PowerMonitor() {
     }
 
-    public static void onBatteryChargingChanged(Intent intent) {
-        if (sInstance == null) {
-            // We may be called by the framework intent-filter before being fully initialized. This
-            // is not a problem, since our constructor will check for the state later on.
-            return;
-        }
+    private static void onBatteryChargingChanged(Intent intent) {
+        assert sInstance != null;
         int chargePlug = intent.getIntExtra(BatteryManager.EXTRA_PLUGGED, -1);
         // If we're not plugged, assume we're running on battery power.
         sInstance.mIsBatteryPower = chargePlug != BatteryManager.BATTERY_PLUGGED_USB
                 && chargePlug != BatteryManager.BATTERY_PLUGGED_AC;
         nativeOnBatteryChargingChanged();
     }
 
     @CalledByNative
     private static boolean isBatteryPower() {
+        // Creation of the PowerMonitor can be deferred based on the browser startup path.  If the
+        // battery power is requested prior to the browser triggering the creation, force it to be
+        // created now.
+        if (sInstance == null) create();
+
         return sInstance.mIsBatteryPower;
     }
 
     private static native void nativeOnBatteryChargingChanged();
 }