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

extensions/common/consumer.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 EXTENSIONS_COMMON_CONSUMER_H_
+#define EXTENSIONS_COMMON_CONSUMER_H_
+
+#include <string>
+
+#include "base/macros.h"
+
+// The type of a host who contains regular tabs or <webview>s.
+enum HostType { EXTENSIONS, WEBUI };

[Fady Samuel, 2015/01/06 13:55:11]

Do we support enum classes in chromium?

[Xi Han, 2015/01/07 18:57:04]

Good point, I think there is example about enum classes, but it is better to
define it within ConsumerID. Moved.

+
+enum InstanceType { TAB, WEBVIEW };
+
+// IDs of API consumers who own user scripts.
+// For example: an extension, a <webview> created by an extension,
+// a <webview> created by WebUI, ...
+struct ConsumerID {
+  // Default instance ID of a consumer who owns staticlly-defined user scripts.
+  static const int kDefaultInstanceID;
+
+  ConsumerID();
+  ConsumerID(HostType host_type,

[Fady Samuel, 2015/01/06 13:55:11]

Once we create a ConsumerID, do its fields ever change? If not, maybe it makes
sense to enforce that?

Maybe we can make this thing a class, make all the fields const privates, and
only add getter accessors?

[Xi Han, 2015/01/07 18:57:04]

As discussed offline, declare ConsumerID as a class, and only add getters. 

+             const std::string& host_id,
+             InstanceType instance_type,
+             int instance_id);
+
+  bool operator<(const ConsumerID& id) const;
+
+  // Extension, or WebUI, ...
+  HostType host_type;
+
+  // Similar to extension_id, host_id is a uniquely indentifier for a host,
+  // e.g., an Extension or WebUI.
+  std::string host_id;
+
+  // A tab or a <webiew>

[Fady Samuel, 2015/01/06 13:55:11]

period at the end of the comment.

[Xi Han, 2015/01/07 18:57:04]

Done.

+  InstanceType instance_type;
+
+  // For a consumer who owns staticlly-defined user scripts, the

[Fady Samuel, 2015/01/06 13:55:11]

For a consumer that owns statically defined user scripts, the |instance_id| is
0.

[Xi Han, 2015/01/07 18:57:04]

Done.

+  // |instance_id| = 0;
+  // For a consumer who owns declarative user scripts, the |instance_id|

[Fady Samuel, 2015/01/06 13:55:11]

change who to that.

[Xi Han, 2015/01/07 18:57:06]

Done.

+  // is assigned by DeclarativeUserScriptManager when the consumer requests a
+  // master object.
+  int instance_id;
+};
+
+// Represents an API consumer.
+class Consumer {
+ public:
+  Consumer();
+  virtual ~Consumer();
+
+  void set_id(const ConsumerID& id) { id_ = id; }

[Fady Samuel, 2015/01/06 13:55:11]

Why is the ConsumerID not in the constructor?

[Xi Han, 2015/01/07 18:57:06]

Think about it again, I remove the member variable ConsumerID id_ from class
Consumer for now. The Consumer is more likely an embedder that holds the
entities who request the API. We can consider extensions is an embedder, and it
is created before the a ConsumerID is produced for script injection. ConsumerID
will be used to represent the entities (e.g., <webview>, tab,...), and Consumer
will just be an interface to represent all kinds of embedders. I will just leave
it as it is now, and maybe update it when more functionalities are needed in the
following CLs.

+  const ConsumerID& id() const { return id_; }
+
+ private:
+  ConsumerID id_;
+
+  DISALLOW_COPY_AND_ASSIGN(Consumer);
+};
+
+#endif  // EXTENSIONS_COMMON_CONSUMER_H_