Refactoring: de-couple Extensions from "script injection System" [render side] : 1

extensions/common/host_id.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 EXTENSIONS_COMMON_HOST_ID_H_
 #define EXTENSIONS_COMMON_HOST_ID_H_
 
 #include <string>
 
 // IDs of hosts who own user scripts.
 // A HostID is immutable after creation.
 struct HostID {
   enum HostType { EXTENSIONS, WEBUI };
 
-  HostID() {}
-  HostID(HostType type, const std::string& id)
-      : type_(type), id_(id) {}
+  HostID();
+  HostID(HostType type, const std::string& id);
+  HostID(const HostID& host_id);
+  ~HostID();
 
-  bool operator<(const HostID& host_id) const {
-    if (type_ != host_id.type())
-      return type_ < host_id.type();
-    else if (id_ != host_id.id())
-      return id_ < host_id.id();
-    return false;
-  }
+  bool operator<(const HostID& host_id) const;
+  bool operator==(const HostID& host_id) const;
 
   HostType type() const { return type_; }
   const std::string& id() const { return id_; }
 
  private:
   // The type of the host.
   HostType type_;
 
   // Similar to extension_id, host_id is a unique indentifier for a host,
   // e.g., an Extension or WebUI.
   std::string id_;
 };
 
 #endif  // EXTENSIONS_COMMON_HOST_ID_H_