Add TabManager class, relocate Tab to common/.

blimp/engine/common/tab_manager.h

Index: blimp/engine/common/tab_manager.h
diff --git a/blimp/engine/common/tab_manager.h b/blimp/engine/common/tab_manager.h
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index 0000000000000000000000000000000000000000..35d0109caf2355fe6aa995fc5001ef07b685c6ad
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+++ b/blimp/engine/common/tab_manager.h
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+// 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 BLIMP_ENGINE_COMMON_TAB_MANAGER_H_
+#define BLIMP_ENGINE_COMMON_TAB_MANAGER_H_
+
+#include <map>
+#include <memory>
+
+#include "base/containers/small_map.h"
+#include "base/macros.h"
+#include "base/observer_list.h"
+
+namespace content {
+class WebContents;
+}
+
+namespace blimp {
+namespace engine {
+
+class Tab;
+
+// Container class for tabs, which are addressable by their ID and WebContents.
+class TabManager {
+ public:
+  TabManager();
+  ~TabManager();
+
+  void Add(std::unique_ptr<Tab> tab);
+  void Remove(Tab* tab);
+  void Clear();
+
+  // Finds a tab with the ID matching |tab_id|.
+  // Returns nullptr if the tab does not exist.
+  Tab* FindTabById(int tab_id) const;
+
+  // Finds the tab which owns |contents|.
+  // Returns nullptr if such a tab does not exist.
+  Tab* FindTabByWebContents(content::WebContents* contents) const;
+
+  // Transitional method, to be used while other features are rewritten to
+  // support multiple tab IDs. Should be removed ASAP.
+  Tab* GetOnlyTab() const;
+
+ private:
+  // Map of tabs, indexed by tab ID.
+  base::SmallMap<int, std::unique_ptr<Tab>> tabs_;
+
+  // Tabs, indexed by WebContents.
+  base::SmallMap<content::WebContents*, Tab*> tabs_by_webcontents_;
+
+  DISALLOW_COPY_AND_ASSIGN(TabManager);
+};
+
+}  // namespace engine
+}  // namespace blimp
+
+#endif  // BLIMP_ENGINE_COMMON_TAB_MANAGER_H_