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

extensions/common/consumer_id.h

Index: extensions/common/consumer_id.h
diff --git a/extensions/common/consumer_id.h b/extensions/common/consumer_id.h
new file mode 100644
index 0000000000000000000000000000000000000000..ba7b5a768f5dc79191cbc670bf6ec5aaf48e63e2
--- /dev/null
+++ b/extensions/common/consumer_id.h
@@ -0,0 +1,65 @@
+// 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_CONSUMER_ID_H_
+#define EXTENSIONS_COMMON_CONSUMER_ID_H_
+
+#include <string>
+
+#include "base/macros.h"
+
+// IDs of API consumers who own user scripts.
+// A ConsumerID is immutable after creation.
+// A ConsumerID could be used for an extension, a <webview> created by an
+// extension, or a <webview> created by WebUI.
+class ConsumerID {
+ public:
+  // The type of a host who contains regular tabs or <webview>s.
+  enum HostType { EXTENSIONS, WEBUI };
+
+  enum InstanceType { TAB, WEBVIEW };
+
+  ConsumerID();
+  ConsumerID(HostType host_type,

[Devlin, 2015/01/21 23:25:21]

Hmm... I think we want to make it clear that most callers shouldn't use this
constructor.  A comment would probably do the trick ("// Only use this
constructor for (de)serialization.").  Otherwise, you could also make ConsumerID
know how to pickle/unpickle itself - which isn't a bad idea, either, and is a
little more OO.

I'll let you decide.

[Xi Han, 2015/01/22 17:19:36]

I slightly prefer to add the common here. I believe this constructor will be
used in the render side when they receive IPC message from the browser and
reconstruct ConsumerID.

+             const std::string& host_id,
+             InstanceType instance_type,
+             int instance_idte);

[Devlin, 2015/01/21 23:25:20]

typo: instance_idte

[Xi Han, 2015/01/22 17:19:36]

Updated.

+  // A constructor to generate |instance_id| based the flag |is_declarative|.
+  // It hides the details how the |instance_id| is assigned:
+  // if |is_declarative| is false, |instance_id| is 0;
+  // otherwise, |instance_id| will be the next available instance id number.
+  ConsumerID(HostType host_type,
+             const std::string& host_id,
+             InstanceType instance_type,
+             bool is_declarative);
+  ~ConsumerID();
+
+  bool operator<(const ConsumerID& id) const;
+  void operator=(const ConsumerID& id);
+
+  HostType host_type() const { return host_type_; }
+  const std::string& host_id() const { return host_id_; }
+  InstanceType instance_type() const { return instance_type_; }
+  int instance_id() const { return instance_id_; }
+
+ private:
+  // The host type of the consumer.
+  HostType host_type_;
+
+  // Similar to extension_id, host_id is a unique indentifier for a host,
+  // e.g., an Extension or WebUI.
+  std::string host_id_;
+
+  // The instance type of the consumer.
+  InstanceType instance_type_;
+
+  // For a consumer that owns staticlly defined user scripts, the

[Devlin, 2015/01/21 23:25:20]

typo: staticlly -> statically

[Xi Han, 2015/01/22 17:19:36]

Done.

+  // |instance_id| is 0.
+  // For a consumer that owns declarative user scripts, the |instance_id|
+  // is assigned by DeclarativeUserScriptManager when the consumer requests a
+  // master object.
+  int instance_id_;
+};
+
+#endif  // EXTENSIONS_COMMON_CONSUMER_ID_H_