[NTP Snippets] Schedule periodic fetching

chrome/browser/android/ntp_snippets_launcher.h

+// Copyright 2016 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_NTP_SNIPPETS_LAUNCHER_H_
+#define CHROME_BROWSER_ANDROID_NTP_SNIPPETS_LAUNCHER_H_
+
+#include "base/android/jni_android.h"
+#include "base/lazy_instance.h"
+#include "base/macros.h"
+#include "components/ntp_snippets/ntp_snippets_scheduler.h"
+
+// Android implementation of ntp_snippets::NTPSnippetsScheduler.
+// The NTPSnippetsLauncher singleton owns the Java SnippetsLauncher object, and
+// is used to schedule the fetching of snippets. Runs on the UI thread.
+class NTPSnippetsLauncher : public ntp_snippets::NTPSnippetsScheduler {
+ public:
+  static NTPSnippetsLauncher* Get();
+
+  static bool Register(JNIEnv* env);
+
+  // ntp_snippets::NTPSnippetsScheduler implementation.
+  bool Schedule(int period_seconds) override;
+  bool Unschedule() override;
+
+ private:
+  friend struct base::DefaultLazyInstanceTraits<NTPSnippetsLauncher>;
+
+  // Constructor and destructor marked private to enforce singleton.
+  NTPSnippetsLauncher();
+  virtual ~NTPSnippetsLauncher();
+
+  base::android::ScopedJavaGlobalRef<jobject> java_launcher_;
+
+  DISALLOW_COPY_AND_ASSIGN(NTPSnippetsLauncher);
+};
+
+#endif  // CHROME_BROWSER_ANDROID_NTP_SNIPPETS_LAUNCHER_H_