The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/ac940cb6160ade6899f326ddde2d180b14e02f4f

commit ac940cb6160ade6899f326ddde2d180b14e02f4f
Author: jianli <jianli@chromium.org>
Date: Wed Jun 07 05:13:08 2017

[Offline Prefetch] Backoff support for PrefetchBackgroundTask

Make PrefetchBackgroundTask support exponential backoff which is saved
to prefs store.

BUG= 727905 
TEST=new tests

Review-Url: https://codereview.chromium.org/2914703002
Cr-Commit-Position: refs/heads/master@{#477553}

[modify] https://crrev.com/ac940cb6160ade6899f326ddde2d180b14e02f4f/chrome/android/java/src/org/chromium/chrome/browser/offlinepages/prefetch/PrefetchBackgroundTask.java
[modify] https://crrev.com/ac940cb6160ade6899f326ddde2d180b14e02f4f/chrome/android/java_sources.gni
[add] https://crrev.com/ac940cb6160ade6899f326ddde2d180b14e02f4f/chrome/android/javatests/src/org/chromium/chrome/browser/offlinepages/prefetch/PrefetchBackgroundTaskTest.java
[rename] https://crrev.com/ac940cb6160ade6899f326ddde2d180b14e02f4f/chrome/android/junit/src/org/chromium/chrome/browser/offlinepages/prefetch/PrefetchBackgroundTaskUnitTest.java
[modify] https://crrev.com/ac940cb6160ade6899f326ddde2d180b14e02f4f/chrome/browser/android/offline_pages/prefetch/prefetch_background_task.cc
[modify] https://crrev.com/ac940cb6160ade6899f326ddde2d180b14e02f4f/chrome/browser/android/offline_pages/prefetch/prefetch_background_task.h
[modify] https://crrev.com/ac940cb6160ade6899f326ddde2d180b14e02f4f/chrome/browser/prefs/browser_prefs.cc
[modify] https://crrev.com/ac940cb6160ade6899f326ddde2d180b14e02f4f/chrome/browser/ui/webui/offline/offline_internals_ui_message_handler.cc
[modify] https://crrev.com/ac940cb6160ade6899f326ddde2d180b14e02f4f/chrome/common/BUILD.gn
[modify] https://crrev.com/ac940cb6160ade6899f326ddde2d180b14e02f4f/chrome/common/DEPS
[modify] https://crrev.com/ac940cb6160ade6899f326ddde2d180b14e02f4f/chrome/common/pref_names.cc
[modify] https://crrev.com/ac940cb6160ade6899f326ddde2d180b14e02f4f/chrome/common/pref_names.h
[modify] https://crrev.com/ac940cb6160ade6899f326ddde2d180b14e02f4f/components/background_task_scheduler/android/java/src/org/chromium/components/background_task_scheduler/BackgroundTaskScheduler.java
[modify] https://crrev.com/ac940cb6160ade6899f326ddde2d180b14e02f4f/components/background_task_scheduler/android/java/src/org/chromium/components/background_task_scheduler/BackgroundTaskSchedulerDelegate.java
[modify] https://crrev.com/ac940cb6160ade6899f326ddde2d180b14e02f4f/components/offline_pages/core/prefetch/prefetch_dispatcher.h
[modify] https://crrev.com/ac940cb6160ade6899f326ddde2d180b14e02f4f/components/offline_pages/core/prefetch/prefetch_dispatcher_impl.cc
[modify] https://crrev.com/ac940cb6160ade6899f326ddde2d180b14e02f4f/components/offline_pages/core/prefetch/prefetch_dispatcher_impl.h
[modify] https://crrev.com/ac940cb6160ade6899f326ddde2d180b14e02f4f/components/offline_pages/core/prefetch/suggested_articles_observer_unittest.cc