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

extensions/common/consumer.cc

+// 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.
+
+#include "extensions/common/consumer.h"
+
+namespace {
+static int current_instance_id_ = ConsumerID::kDefaultInstanceID;

[Devlin, 2015/01/20 17:51:06]

anonymous namespace + static = redundant.

[Devlin, 2015/01/20 17:51:06]

We should probably use a StaticAtomicSequenceNumber for this (see user_script.cc
for an example).

[Xi Han, 2015/01/21 21:30:17]

Removed.

[Xi Han, 2015/01/21 21:30:17]

As discussed offline, will still use int for current_instance_id_.

+}
+
+const int ConsumerID::kDefaultInstanceID = 0;
+
+ConsumerID::ConsumerID() {
+}
+
+ConsumerID::ConsumerID(const ConsumerID& other)
+    : host_type_(other.host_type()),
+      host_id_(other.host_id()),
+      instance_type_(other.instance_type()),
+      instance_id_(other.instance_id()) {
+}
+
+ConsumerID::ConsumerID(HostType host_type,
+                       const std::string& host_id,
+                       InstanceType instance_type,
+                       int instance_id)
+    : host_type_(host_type),
+      host_id_(host_id),
+      instance_type_(instance_type),
+      instance_id_(instance_id) {
+}
+
+// static
+int ConsumerID::GetNextID() {
+  return ++current_instance_id_;
+}
+
+bool ConsumerID::operator<(const ConsumerID& id) const {
+  return host_type_ < id.host_type() ||
+         (host_type_ == id.host_type() && host_id_.compare(id.host_id()) < 0) ||

[Devlin, 2015/01/20 17:51:06]

yuck :/  Why isn't there a better way to do this yet?  I mean, you can cheat
with std::tie, but that's just...weird.

I think this is easier to read, and not any more lines, as:
if (host_type_ != id.host_type_)
  return host_type_ < id.host_type_;
if (host_id_ != id.host_id_)
  return host_id_ < id.host_id_;
...

[Xi Han, 2015/01/21 21:30:17]

Yes, the code seems easier to understand now. 

+         (host_type_ == id.host_type() && host_id_.compare(id.host_id()) == 0 &&
+          instance_type_ < id.instance_type()) ||
+         (host_type_ == id.host_type() && host_id_.compare(id.host_id()) == 0 &&
+          instance_type_ == id.instance_type() &&
+          instance_id_ < id.instance_id());
+}
+
+void ConsumerID::operator=(const ConsumerID& id) {
+  host_type_ = id.host_type();
+  host_id_ = id.host_id();
+  instance_type_ = id.instance_type();
+  instance_id_ = id.instance_id();
+}
+
+ConsumerID::~ConsumerID() {
+}
+
+Consumer::Consumer() {
+}
+
+Consumer::~Consumer() {
+}