Reland of [Background Sync] Trigger Background Sync events when Chrome is backgrounded on Android

content/browser/background_sync/background_sync_network_observer.h

 // 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.
 
 #ifndef CONTENT_BROWSER_BACKGROUND_SYNC_BACKGROUND_SYNC_NETWORK_OBSERVER_H_
 #define CONTENT_BROWSER_BACKGROUND_SYNC_BACKGROUND_SYNC_NETWORK_OBSERVER_H_
 
 #include "base/bind.h"
 #include "content/browser/background_sync/background_sync.pb.h"
 #include "content/common/content_export.h"
 #include "net/base/network_change_notifier.h"
 
 namespace content {
 
 class CONTENT_EXPORT BackgroundSyncNetworkObserver
-    : net::NetworkChangeNotifier::NetworkChangeObserver {
+    : public net::NetworkChangeNotifier::NetworkChangeObserver {
  public:
   // Creates a BackgroundSyncNetworkObserver. |network_changed_callback| is
   // called when the network connection changes asynchronously via PostMessage.
   BackgroundSyncNetworkObserver(const base::Closure& network_changed_callback);
 
   ~BackgroundSyncNetworkObserver() override;
 
+  // Enable or disable notifications coming from the NetworkChangeNotifier. (For
+  // preventing flakes in tests)
+  static void SetIgnoreNetworkChangeNotifierForTests(bool ignore);
+
   // Returns true if the state of the network meets the needs of
   // |network_state|.
   bool NetworkSufficient(SyncNetworkState network_state);
 
- private:
-  void NotifyNetworkChanged();
-
   // NetworkChangeObserver overrides
   void OnNetworkChanged(
       net::NetworkChangeNotifier::ConnectionType connection_type) override;
 
+ private:
+  friend class BackgroundSyncBrowserTest;
+  friend class BackgroundSyncManagerTest;
+
+  // Calls NotifyNetworkChanged if the connection type has changed.
+  void NotifyManagerIfNetworkChanged(
+      net::NetworkChangeNotifier::ConnectionType connection_type);
+
+  void NotifyNetworkChanged();
+
   net::NetworkChangeNotifier::ConnectionType connection_type_;
 
   // The callback to run when the network changes.
   base::Closure network_changed_callback_;
 
+  // Set true to ignore notifications coming from the NetworkChangeNotifier
+  // (to prevent flakes in tests).
+  static bool ignore_network_change_notifier_;
+
   DISALLOW_COPY_AND_ASSIGN(BackgroundSyncNetworkObserver);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_BACKGROUND_SYNC_BACKGROUND_SYNC_NETWORK_OBSERVER_H_