Introduce DeclarativeUserScriptManager.

chrome/browser/extensions/declarative_user_script_manager.h

+// Copyright 2014 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_EXTENSIONS_DECLARATIVE_USER_SCRIPT_MANAGER_H_
+#define CHROME_BROWSER_EXTENSIONS_DECLARATIVE_USER_SCRIPT_MANAGER_H_
+
+#include <map>
+
+#include "base/macros.h"
+#include "base/memory/linked_ptr.h"
+
+class Profile;
+
+namespace extensions {

[Devlin, 2014/12/12 20:02:45]

hmm... actually, for as long as this class is in c/b/extensions, let's leave it
in the extensions namespace for consistency.

[Xi Han, 2014/12/12 20:32:31]

That is ok, add the namespace back.

+class DeclarativeUserScriptMaster;
+}
+
+using UserScriptMasterMap =

[Devlin, 2014/12/12 20:02:45]

nit: When I mentioned this should go above class members, I just meant it should
be above the member variables (i.e., it should be above
declarative_user_script_masters_ and profile_).  You were right with putting it
in the private: section of the class. :)

[Xi Han, 2014/12/12 20:32:31]

Done.

+std::map<std::string, linked_ptr<extensions::DeclarativeUserScriptMaster>>;
+
+// Manages a set of DeclarativeUserScriptMaster objects for script injections.
+class DeclarativeUserScriptManager {
+ public:
+  explicit DeclarativeUserScriptManager(Profile* profile);
+  ~DeclarativeUserScriptManager();
+
+  // Get the user script master for declarative scripts; if does not exist, a

[Devlin, 2014/12/12 20:02:45]

nit: "if one does not exist" instead of "if does not exist".

[Xi Han, 2014/12/12 20:32:31]

Done.

[Xi Han, 2014/12/12 20:32:31]

Done.

+  // new object will be created.
+  extensions::DeclarativeUserScriptMaster* GetDeclarativeUserScriptMasterByID(
+      const std::string& id);
+
+ private:
+  // Manages a set of DeclarativeUserScript objects for programmatically

[Devlin, 2014/12/12 20:02:45]

This seems more like a comment of the full class (DeclarativeUserScriptManager),
rather than the map.  Maybe just "A map of DeclarativeUserScriptMasters for ids;
each master is lazily initialized."?

[Xi Han, 2014/12/12 20:32:31]

Sounds better. Updated.

+  // declared scripts. The objects are instantiated lazily.
+  UserScriptMasterMap declarative_user_script_masters_;
+
+  Profile* profile_;
+
+  DISALLOW_COPY_AND_ASSIGN(DeclarativeUserScriptManager);
+};
+
+#endif  // CHROME_BROWSER_EXTENSIONS_DECLARATIVE_USER_SCRIPT_MANAGER_H_