Record UMA for battery level when precache starts and ends

chrome/android/java/src/org/chromium/chrome/browser/precache/PrecacheController.java

 // Copyright 2015 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.chrome.browser.precache;
 
 import android.content.BroadcastReceiver;
 import android.content.Context;
 import android.content.Intent;
 import android.content.IntentFilter;
@@ skipping 351 matching lines @@
             cancelPeriodicPrecacheTask(mAppContext);
             cancelPrecacheCompletionTask(mAppContext);
             PrecacheUMA.record(PrecacheUMA.Event.DISABLED_IN_PRECACHE_PREF);
             return GcmNetworkManager.RESULT_SUCCESS;
         }
         if (setIsPrecaching(true)) {
             if (PERIODIC_TASK_TAG.equals(tag)) {
                 recordPeriodicTaskIntervalHistogram();
                 cancelPrecacheCompletionTask(mAppContext);
             }
+            recordBatteryLevelAtStart();
             registerDeviceStateReceiver();
             acquirePrecachingWakeLock();
             startPrecachingAfterSyncInit();
             return GcmNetworkManager.RESULT_SUCCESS;
         }
         Log.v(TAG, "precache session was already running");
         PrecacheUMA.record(PrecacheUMA.Event.PRECACHE_TASK_STARTED_DUPLICATE);
         return GcmNetworkManager.RESULT_FAILURE;
     }
 
@@ skipping 50 matching lines @@
 
     /**
      * Updates state to indicate that the precache session is no longer in
      * progress, and stops the service.
      */
     private void shutdownPrecaching(boolean precachingIncomplete) {
         Log.v(TAG, "shutting down precache session");
         if (precachingIncomplete) {
             schedulePrecacheCompletionTask(mAppContext);
         }
+        recordBatteryLevelAtEnd();
         mHandler.removeCallbacks(mTimeoutRunnable);
         mAppContext.unregisterReceiver(mDeviceStateReceiver);
         releasePrecachingWakeLock();
     }
 
     /**
      * Registers a BroadcastReceiver to detect when conditions become wrong
      * for precaching.
      */
     private void registerDeviceStateReceiver() {
@@ skipping 84 matching lines @@
         if (previous_start_time_ms > 0 && current_start_time_ms > previous_start_time_ms) {
             int interval_mins =
                     (int) ((current_start_time_ms - previous_start_time_ms) / (1000 * 60));
             RecordHistogram.recordCustomCountHistogram(
                     "Precache.PeriodicTaskInterval", interval_mins, 1, 10000, 50);
         }
         prefs.edit()
                 .putLong(PREF_PRECACHE_PERIODIC_TASK_START_TIME_MS, current_start_time_ms)
                 .apply();
     }
+
+    private void recordBatteryLevelAtStart() {
+        mDeviceState.saveCurrentBatteryPercentage(mAppContext);
+
+        // Report battery percentage.
+        RecordHistogram.recordPercentageHistogram(
+                "Precache.BatteryPercentage.Start", mDeviceState.getSavedBatteryPercentage());
+    }
+
+    private void recordBatteryLevelAtEnd() {
+        int delta_percentage = mDeviceState.getCurrentBatteryPercentage(mAppContext)
+                - mDeviceState.getSavedBatteryPercentage();
+        if (delta_percentage >= 0) {
+            RecordHistogram.recordPercentageHistogram(
+                    "Precache.BatteryPercentageDiff.End", delta_percentage);
+        }
+    }
 }