Record UMA for battery level when precache starts and ends

components/precache/android/java/src/org/chromium/components/precache/DeviceState.java

Index: components/precache/android/java/src/org/chromium/components/precache/DeviceState.java
diff --git a/components/precache/android/java/src/org/chromium/components/precache/DeviceState.java b/components/precache/android/java/src/org/chromium/components/precache/DeviceState.java
index 1a63a26a87b00b84882735e5daf7f8ba319c9236..8027a3f2aa605477a88a638189c040f04f41a3d1 100644
--- a/components/precache/android/java/src/org/chromium/components/precache/DeviceState.java
+++ b/components/precache/android/java/src/org/chromium/components/precache/DeviceState.java
@@ -17,6 +17,9 @@ import org.chromium.base.VisibleForTesting;
 public class DeviceState {
     private static DeviceState sDeviceState = null;
 
+    // Saved battery level percentage.
+    private int mSavedBatteryPercentage = 0;
+
     /** Disallow Construction of DeviceState objects. Use {@link #getInstance()} instead to create
      * a singleton instance.
      */
@@ -58,6 +61,36 @@ public class DeviceState {
                 || status == BatteryManager.BATTERY_STATUS_FULL;
     }
 
+    /**
+     * @return the previously saved battery level percentage.
+     * @param context the application context
+     */
+    public int getSavedBatteryPercentage() {
+        return mSavedBatteryPercentage;
+    }
+
+    /**
+     * Saves the current battery level percentage to be retrieved later.
+     */
+    public void saveCurrentBatteryPercentage(Context context) {
+        mSavedBatteryPercentage = getCurrentBatteryPercentage(context);
+    }
+
+    /**
+     * @return the current battery level as percentage.
+     * @param context the application context
+     */
+    public int getCurrentBatteryPercentage(Context context) {
+        IntentFilter iFilter = new IntentFilter(Intent.ACTION_BATTERY_CHANGED);
+        Intent batteryStatus = context.registerReceiver(null, iFilter);
+        if (batteryStatus == null) return 0;
+        int level = batteryStatus.getIntExtra(BatteryManager.EXTRA_LEVEL, -1);
+        int scale = batteryStatus.getIntExtra(BatteryManager.EXTRA_SCALE, -1);
+        if (scale == 0) return 0;
+
+        return Math.round(100 * level / (float) scale);
+    }
+
     /** @return whether the currently active network is unmetered. */
     public boolean isUnmeteredNetworkAvailable(Context context) {
         NetworkInfoDelegate networkInfo =