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

extensions/common/consumer.cc

Index: extensions/common/consumer.cc
diff --git a/extensions/common/consumer.cc b/extensions/common/consumer.cc
new file mode 100644
index 0000000000000000000000000000000000000000..66f2ab3a03382b869057aa6f48503fc17238eef2
--- /dev/null
+++ b/extensions/common/consumer.cc
@@ -0,0 +1,63 @@
+// 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 "base/memory/scoped_ptr.h"
+#include "extensions/common/consumer.h"
+
+namespace {
+static int current_instance_id_ = ConsumerID::kDefaultInstanceID;
+static scoped_ptr<ConsumerID> empty_consumer_id;
+}
+
+const int ConsumerID::kDefaultInstanceID = 0;
+
+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) {
+}
+
+const ConsumerID& ConsumerID::EmptyConsumerID() {
+  if (!empty_consumer_id.get()) {
+    empty_consumer_id.reset(new ConsumerID(
+        ConsumerID::EXTENSIONS, std::string(),
+        ConsumerID::TAB, ConsumerID::kDefaultInstanceID));
+  }
+  return *empty_consumer_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) ||
+         (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());
+}
+
+ConsumerID::~ConsumerID() {
+}
+
+Consumer::Consumer() {
+}
+
+Consumer::~Consumer() {
+}