Add a way to send the resource percentage signal to the RC.

components/offline_pages/core/background/resource_tracker_observer.h

Index: components/offline_pages/core/background/resource_tracker_observer.h
diff --git a/components/offline_pages/core/background/resource_tracker_observer.h b/components/offline_pages/core/background/resource_tracker_observer.h
new file mode 100644
index 0000000000000000000000000000000000000000..18ce6cad32d64ae0b2e221a66e11c22a7d8415fa
--- /dev/null
+++ b/components/offline_pages/core/background/resource_tracker_observer.h
@@ -0,0 +1,27 @@
+// 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 COMPONENTS_OFFLINE_PAGES_CORE_BACKGROUND_RESOURCE_TRACKER_OBSERVER_H_
+#define COMPONENTS_OFFLINE_PAGES_CORE_BACKGROUND_RESOURCE_TRACKER_OBSERVER_H_
+
+#include <stdint.h>
+
+#include "components/offline_pages/core/background/resource_data_type.h"
+
+namespace offline_pages {
+
+// Interface for observing notifications from the resource tracker start and
+// completion counts.
+class ResourceTrackerObserver {
+ public:
+  // When we are notified of a resource load starting or ending, pass the
+  // information along to the offliner.
+  virtual void ObserveResourceTracking(const ResourceDataType type,
+                                       int64_t started_count,
+                                       int64_t completed_count) = 0;
+};
+
+}  // namespace offline_pages
+
+#endif  // COMPONENTS_OFFLINE_PAGES_CORE_BACKGROUND_RESOURCE_TRACKER_OBSERVER_H_