Introduce HostID and de-couple Extensions from "script injection System" [browser side]

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>
+
+#include "base/macros.h"
+
+// IDs of hosts who own user scripts.
+// A HostID is immutable after creation.
+struct HostID {
+  enum HostType { EXTENSIONS, WEBUI };
+
+  HostID() {}
+  HostID(HostType host_type, const std::string& host_id)
+      : type(host_type), id(host_id) {}
+
+  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();
+    else
+      return false;
+  }
+
+  HostType Type() const { return type; }

[Devlin, 2015/01/26 20:12:09]

nit: lowercase these -> type() and id()

[Xi Han, 2015/01/26 23:27:53]

Done.

+  const std::string& ID() const { return id; }
+
+ private:
+  // The type of the host.
+  HostType type;

[Devlin, 2015/01/26 20:12:09]

Since these are private, they should have a trailing _

[Xi Han, 2015/01/26 23:27:53]

Oh, I thought the member variables of a struct wouldn't have a trailing _.
Updated.

+
+  // 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_