capping how many times background download resumption can automatically start

chrome/android/java/src/org/chromium/chrome/browser/download/DownloadNotificationService.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.download;
 
 import android.app.Notification;
 import android.app.NotificationManager;
 import android.app.PendingIntent;
 import android.app.Service;
@@ skipping 44 matching lines @@
     public static final String ACTION_DOWNLOAD_RESUME_ALL =
             "org.chromium.chrome.browser.download.DOWNLOAD_RESUME_ALL";
     static final int INVALID_DOWNLOAD_PERCENTAGE = -1;
     @VisibleForTesting
     static final String PENDING_DOWNLOAD_NOTIFICATIONS = "PendingDownloadNotifications";
     static final String NOTIFICATION_NAMESPACE = "DownloadNotificationService";
     private static final String TAG = "DownloadNotification";
     private static final String NEXT_DOWNLOAD_NOTIFICATION_ID = "NextDownloadNotificationId";
     // Notification Id starting value, to avoid conflicts from IDs used in prior versions.
     private static final int STARTING_NOTIFICATION_ID = 1000000;
+    private static final String AUTO_RESUMPTION_ATTEMPT_LEFT = "ResumptionAttemptLeft";
+    private static final int MAX_RESUMPTION_ATTEMPT_LEFT = 5;
     @VisibleForTesting static final int SECONDS_PER_MINUTE = 60;
     @VisibleForTesting static final int SECONDS_PER_HOUR = 60 * 60;
     @VisibleForTesting static final int SECONDS_PER_DAY = 24 * 60 * 60;
     private final IBinder mBinder = new LocalBinder();
     private final List<DownloadSharedPreferenceEntry> mDownloadSharedPreferenceEntries =
             new ArrayList<DownloadSharedPreferenceEntry>();
     private final List<String> mDownloadsInProgress = new ArrayList<String>();
     private NotificationManager mNotificationManager;
     private SharedPreferences mSharedPrefs;
     private Context mContext;
     private int mNextNotificationId;
+    private int mNumAutoResumptionAttemptLeft;
 
     /**
      * Class for clients to access.
      */
     public class LocalBinder extends Binder {
         DownloadNotificationService getService() {
             return DownloadNotificationService.this;
         }
     }
 
@@ skipping 33 matching lines @@
      */
     private void onBrowserKilled() {
         pauseAllDownloads();
         if (!mDownloadSharedPreferenceEntries.isEmpty()) {
             boolean allowMeteredConnection = false;
             for (int i = 0; i < mDownloadSharedPreferenceEntries.size(); ++i) {
                 if (mDownloadSharedPreferenceEntries.get(i).canDownloadWhileMetered) {
                     allowMeteredConnection = true;
                 }
             }
-            DownloadResumptionScheduler.getDownloadResumptionScheduler(mContext).schedule(
-                    allowMeteredConnection);
+            if (mNumAutoResumptionAttemptLeft > 0) {
+                DownloadResumptionScheduler.getDownloadResumptionScheduler(mContext).schedule(
+                        allowMeteredConnection);
+            }
         }
         stopSelf();
     }
 
     @Override
     public int onStartCommand(final Intent intent, int flags, int startId) {
         if (isDownloadOperationIntent(intent)) {
             handleDownloadOperation(intent);
             DownloadResumptionScheduler.getDownloadResumptionScheduler(mContext).cancelTask();
+            // Limit the number of auto resumption attempts in case Chrome falls into a vicious
+            // cycle.
+            if (intent.getAction() == ACTION_DOWNLOAD_RESUME_ALL) {
+                if (mNumAutoResumptionAttemptLeft > 0) {
+                    mNumAutoResumptionAttemptLeft--;
+                    updateResumptionAttemptLeft();
+                }
+            } else {
+                // Reset number of attempts left if the action is triggered by user.
+                mNumAutoResumptionAttemptLeft = MAX_RESUMPTION_ATTEMPT_LEFT;
+                clearResumptionAttemptLeft();
+            }
         }
-
         // This should restart the service after Chrome gets killed. However, this
         // doesn't work on Android 4.4.2.
         return START_STICKY;
     }
 
     @Override
     public IBinder onBind(Intent intent) {
         return mBinder;
     }
 
     /**
+     * Helper method to update the remaining number of background resumption attempts left.
+     * @param attamptLeft Number of attempt left.
+     */
+    private void updateResumptionAttemptLeft() {
+        SharedPreferences.Editor editor = mSharedPrefs.edit();
+        editor.putInt(AUTO_RESUMPTION_ATTEMPT_LEFT, mNumAutoResumptionAttemptLeft);
+        editor.apply();
+    }
+
+    /**
+     * Helper method to clear the remaining number of background resumption attempts left.
+     */
+    static void clearResumptionAttemptLeft() {
+        SharedPreferences SharedPrefs = ContextUtils.getAppSharedPreferences();
+        SharedPreferences.Editor editor = SharedPrefs.edit();
+        editor.remove(AUTO_RESUMPTION_ATTEMPT_LEFT);
+        editor.apply();
+    }
+
+    /**
      * Add a in-progress download notification.
      * @param downloadGuid GUID of the download.
      * @param fileName File name of the download.
      * @param percentage Percentage completed. Value should be between 0 to 100 if
      *        the percentage can be determined, or -1 if it is unknown.
      * @param timeRemainingInMillis Remaining download time in milliseconds.
      * @param startTime Time when download started.
      * @param isResumable Whether the download can be resumed.
      * @param canDownloadWhileMetered Whether the download can happen in metered network.
      */
@@ skipping 378 matching lines @@
             if (!entry.canDownloadWhileMetered && isNetworkMetered) continue;
             if (mDownloadsInProgress.contains(entry.downloadGuid)) continue;
             notifyDownloadProgress(entry.downloadGuid, entry.fileName,
                     INVALID_DOWNLOAD_PERCENTAGE, 0, 0, true, entry.canDownloadWhileMetered);
             service.resumeDownload(entry.buildDownloadItem(), false);
         }
     }
 
     /**
      * Parse the DownloadSharedPreferenceEntry from the shared preference and return a list of them.
      * @return a list of parsed DownloadSharedPreferenceEntry.

[Ted C, 2016/06/27 17:13:07]

update the comment here

[qinmin, 2016/06/27 22:02:33]

Done.

      */
     void parseDownloadSharedPrefs() {
+        mNumAutoResumptionAttemptLeft = mSharedPrefs.getInt(AUTO_RESUMPTION_ATTEMPT_LEFT,
+                MAX_RESUMPTION_ATTEMPT_LEFT);
         if (!mSharedPrefs.contains(PENDING_DOWNLOAD_NOTIFICATIONS)) return;
         Set<String> entries = DownloadManagerService.getStoredDownloadInfo(
                 mSharedPrefs, PENDING_DOWNLOAD_NOTIFICATIONS);
         for (String entryString : entries) {
             DownloadSharedPreferenceEntry entry =
                     DownloadSharedPreferenceEntry.parseFromString(entryString);
             if (entry.notificationId > 0) {
                 mDownloadSharedPreferenceEntries.add(
                         DownloadSharedPreferenceEntry.parseFromString(entryString));
             }
@@ skipping 87 matching lines @@
             return context.getString(R.string.remaining_duration_minutes, minutes);
         } else if (minutes > 0) {
             return context.getString(R.string.remaining_duration_one_minute);
         } else if (seconds == 1) {
             return context.getString(R.string.remaining_duration_one_second);
         } else {
             return context.getString(R.string.remaining_duration_seconds, seconds);
         }
     }
 }