[Offline Prefetch] Create a new JobScheduler task to wake up for net activity.

chrome/browser/android/offline_pages/prefetch/prefetch_background_task.h

+// Copyright 2017 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.
+
+#ifndef CHROME_BROWSER_ANDROID_OFFLINE_PAGES_PREFETCH_PREFETCH_BACKGROUND_TASK_H_
+#define CHROME_BROWSER_ANDROID_OFFLINE_PAGES_PREFETCH_PREFETCH_BACKGROUND_TASK_H_
+
+#include "base/android/jni_android.h"
+#include "components/offline_pages/core/prefetch/prefetch_service.h"
+
+namespace offline_pages {
+
+// A task with a counterpart in Java for managing the background activity of the
+// offline page prefetcher.  Schedules and listens for events about prefetching
+// tasks.
+class PrefetchBackgroundTask : public PrefetchService::ScopedBackgroundTask {

[carlosk, 2017/04/19 23:01:38]

Why is this out of the offline_pages::prefetch namespace?

[dewittj, 2017/04/20 21:41:45]

I invented the offline_pages::prefetch namespace only for the JNI generator,
since it makes a static function with a predictable name and the offline_pages::
namespace already had such a function. I don't intend for all this code to go
into the sub namespace.

+ public:
+  PrefetchBackgroundTask(
+      JNIEnv* env,
+      const base::android::JavaParamRef<jobject>& j_prefetch_background_task,
+      PrefetchService* service);
+  ~PrefetchBackgroundTask() override;
+
+  // API for interacting with JobScheduler from native.
+  // Schedules the default 'NWake' prefetching task.  Does nothing if
+  // JobScheduler is not supported.
+  static void Schedule();
+
+  // Cancels the default 'NWake' prefetching task.  Does nothing if
+  // JobScheduler is not supported.
+  static void Cancel();
+
+  // Java hooks.
+  bool OnStopTask(JNIEnv* env,
+                  const base::android::JavaParamRef<jobject>& jcaller);
+
+  // When this task completes, we tell the system whether the task should be
+  // rescheduled with the same parameters as last time.
+  void SetNeedsReschedule(bool reschedule) override;
+  bool needs_reschedule() { return needs_reschedule_; }
+
+ private:
+  bool needs_reschedule_ = true;
+
+  // A pointer to the controlling |PrefetchBackgroundTask|.
+  base::android::ScopedJavaGlobalRef<jobject> java_prefetch_background_task_;
+
+  // The PrefetchService owns |this|, so a raw pointer is OK.
+  PrefetchService* service_;
+};
+
+bool RegisterPrefetchBackgroundTask(JNIEnv* env);
+
+}  // namespace offline_pages
+
+#endif  // CHROME_BROWSER_ANDROID_OFFLINE_PAGES_PREFETCH_PREFETCH_BACKGROUND_TASK_H_