Fix a bug in UserScriptLoader.

extensions/common/host_id.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/host_id.h"
 
-HostID::HostID() {
+HostID::HostID()
+    : type_(HostType::EXTENSIONS) {
 }
 
 HostID::HostID(HostType type, const std::string& id)
     : type_(type), id_(id) {
 }
 
 HostID::HostID(const HostID& host_id)
     : type_(host_id.type()),
       id_(host_id.id()) {
 }
 
 HostID::~HostID() {
 }
 
 bool HostID::operator<(const HostID& host_id) const {
   if (type_ != host_id.type())
     return type_ < host_id.type();
   else if (id_ != host_id.id())
     return id_ < host_id.id();
   return false;
 }
 
 bool HostID::operator==(const HostID& host_id) const {
   return type_ == host_id.type() && id_ == host_id.id();
 }