[Contextual Search] Add Mojo-enabled API component.

chrome/browser/search/contextual_search_service.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 CHROME_BROWSER_SEARCH_CONTEXTUAL_SEARCH_SERVICE_H_
+#define CHROME_BROWSER_SEARCH_CONTEXTUAL_SEARCH_SERVICE_H_
+
+#include "base/memory/singleton.h"
+#include "content/public/browser/notification_observer.h"
+#include "content/public/browser/notification_registrar.h"
+
+// Provides a singleton service for Contextual Search.
+// Tracks render process host IDs that are associated with ContextualSearch.
+class ContextualSearchService : public content::NotificationObserver {
+ public:
+  static ContextualSearchService* GetInstance();
+
+  // Add, remove, and query RenderProcessHost IDs that are associated with
+  // Contextual Search processes.
+  void SetContextualSearchProcess(int process_id);
+  bool IsContextualSearchProcess(int process_id) const;
+
+ private:
+  // Use GetInstance instead of constructing.
+  ContextualSearchService();
+  ~ContextualSearchService() override;
+
+  // Singleton:
+  friend struct base::DefaultSingletonTraits<ContextualSearchService>;
+
+  // content::NotificationObserver:
+  void Observe(int type,
+               const content::NotificationSource& source,
+               const content::NotificationDetails& details) override;
+
+  void OnRendererProcessTerminated(int process_id);
+
+  // The process id associated with Contextual Search processes.
+  int process_id_;
+
+  content::NotificationRegistrar registrar_;
+
+  DISALLOW_COPY_AND_ASSIGN(ContextualSearchService);
+};
+
+#endif  // CHROME_BROWSER_SEARCH_CONTEXTUAL_SEARCH_SERVICE_H_