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

chrome/browser/extensions/consumer_id_factory.cc

+// 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.
+
+#include "chrome/browser/extensions/consumer_id_factory.h"
+
+#include "base/lazy_instance.h"
+#include "base/memory/linked_ptr.h"
+
+namespace {
+using RequestContentScriptKeyToIDMap =
+    std::map<RequestContentScriptKey, linked_ptr<ConsumerID>>;
+
+// A map of ConsumerIDs for the given RequestContentScript ids.
+// Different types of input ids will define their own maps to store the
+// mappings from ids to ConsumerIDs.
+static base::LazyInstance<RequestContentScriptKeyToIDMap>
+      request_content_script_key_to_id_map_ = LAZY_INSTANCE_INITIALIZER;
+
+int current_instance_id_ = ConsumerID::kDefaultInstanceID;
+
+// Get next available instance ID.
+static int GetNextID() {
+  return ++current_instance_id_;
+}
+
+}  // namespace
+
+// static
+const ConsumerID& ConsumerIDFactory::Create(
+    const RequestContentScriptKey& key,
+    ConsumerID::HostType host_type,
+    ConsumerID::InstanceType instance_type) {
+  RequestContentScriptKeyToIDMap::iterator it =
+      request_content_script_key_to_id_map_.Get().find(key);
+  if (it != request_content_script_key_to_id_map_.Get().end())
+    return *(it->second.get());
+
+  linked_ptr<ConsumerID> consumer_id(new ConsumerID(
+      host_type, key.host_id, instance_type, GetNextID()));
+  request_content_script_key_to_id_map_.Get()[key] = consumer_id;
+  return *(consumer_id.get());
+}
+