Add CombinedDesktopMediaList class

chrome/browser/media/combined_desktop_media_list.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_MEDIA_COMBINED_DESKTOP_MEDIA_LIST_H_
+#define CHROME_BROWSER_MEDIA_COMBINED_DESKTOP_MEDIA_LIST_H_
+
+#include <vector>
+
+#include "base/memory/scoped_ptr.h"
+#include "chrome/browser/media/desktop_media_list.h"
+#include "chrome/browser/media/desktop_media_list_observer.h"
+
+// Combination of different types of DesktopMediaLists.

[Sergey Ulanov, 2016/01/26 18:06:54]

nit: they don't have to be two different types, just some lists.
The comment should also explain how they are being combined into one, i.e. that
the lists are concatenated.

[GeorgeZ, 2016/01/27 00:17:38]

Done.

+class CombinedDesktopMediaList : public DesktopMediaList,
+                                 public DesktopMediaListObserver {
+ public:
+  explicit CombinedDesktopMediaList(
+      std::vector<scoped_ptr<DesktopMediaList>>& media_lists);
+  ~CombinedDesktopMediaList() override;
+
+  // DesktopMediaList interface.
+  void SetUpdatePeriod(base::TimeDelta period) override;
+  void SetThumbnailSize(const gfx::Size& thumbnail_size) override;
+  void SetViewDialogWindowId(content::DesktopMediaID dialog_id) override;
+  void StartUpdating(DesktopMediaListObserver* observer) override;
+  int GetSourceCount() const override;
+  const Source& GetSource(int index) const override;
+
+ private:
+  // DesktopMediaListObserver interface.
+  void OnSourceAdded(DesktopMediaList* list, int index) override;
+  void OnSourceRemoved(DesktopMediaList* list, int index) override;
+  void OnSourceMoved(DesktopMediaList* list,
+                     int old_index,
+                     int new_index) override;
+  void OnSourceNameChanged(DesktopMediaList* list, int index) override;
+  void OnSourceThumbnailChanged(DesktopMediaList* list, int index) override;
+
+  std::vector<scoped_ptr<DesktopMediaList>> media_lists_;
+
+  DesktopMediaListObserver* observer_ = nullptr;
+
+  DISALLOW_COPY_AND_ASSIGN(CombinedDesktopMediaList);
+};
+
+#endif  // CHROME_BROWSER_MEDIA_COMBINED_DESKTOP_MEDIA_LIST_H_