Add the request picker and a unit test

components/offline_pages/background/request_picker.h

Index: components/offline_pages/background/request_picker.h
diff --git a/components/offline_pages/background/request_picker.h b/components/offline_pages/background/request_picker.h
new file mode 100644
index 0000000000000000000000000000000000000000..7e8f318eb009393c57e1baf7044461088659737b
--- /dev/null
+++ b/components/offline_pages/background/request_picker.h
@@ -0,0 +1,43 @@
+// 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 COMPONENTS_OFFLINE_PAGES_BACKGROUND_REQUEST_PICKER_H_
+#define COMPONENTS_OFFLINE_PAGES_BACKGROUND_REQUEST_PICKER_H_
+
+#include "base/memory/weak_ptr.h"
+#include "components/offline_pages/background/request_coordinator.h"
+#include "components/offline_pages/background/request_queue.h"
+
+namespace offline_pages {
+
+class RequestPicker {
+ public:
+  RequestPicker(RequestQueue* requestQueue);
+
+  ~RequestPicker();
+
+  // Choose which request we should process next based on the current
+  // conditions, and call back to the RequestCoordinator when we have one.
+  void ChooseNextRequest(
+      RequestCoordinator::RequestPickedCallback picked_callback,
+      RequestCoordinator::RequestQueueEmptyCallback empty_callback);
+
+ private:
+  // Callback for the GetRequest results to be delivered.
+  void GetRequestResultCallback(RequestQueue::GetRequestsResult result,
+                                const std::vector<SavePageRequest>& results);
+
+  // unowned pointer to the request queue.
+  RequestQueue* queue_;
+  // Callback for when we are done picking a request to do next.
+  RequestCoordinator::RequestPickedCallback picked_callback_;
+  // Callback for when there are no more reqeusts to pick.
+  RequestCoordinator::RequestQueueEmptyCallback empty_callback_;
+  // Allows us to pass a weak pointer to callbacks.
+  base::WeakPtrFactory<RequestPicker> weak_ptr_factory_;
+};
+
+}  // namespace offline_pages
+
+#endif  // COMPONENTS_OFFLINE_PAGES_BACKGROUND_REQUEST_PICKER_H_