Rework some UserScriptLoader logic in preparation to removing UserScript copy.

extensions/common/user_script.cc

 // Copyright 2013 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/user_script.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include "base/atomic_sequence_num.h"
@@ skipping 270 matching lines @@
   uint32_t num_files = 0;
   CHECK(iter->ReadUInt32(&num_files));
   scripts->clear();
   for (uint32_t i = 0; i < num_files; ++i) {
     File file;
     file.Unpickle(pickle, iter);
     scripts->push_back(file);
   }
 }
 
+UserScriptIDPair::UserScriptIDPair(int id, const HostID& host_id)
+    : id(id), host_id(host_id) {}
+
+UserScriptIDPair::UserScriptIDPair(int id) : id(id), host_id(HostID()) {}
+
+bool operator<(const UserScriptIDPair& a, const UserScriptIDPair& b) {
+  return a.id < b.id;
+}
+
 bool operator<(const UserScript& script1, const UserScript& script2) {
   // The only kind of script that should be compared is the kind that has its
   // IDs initialized to a meaningful value.
   DCHECK(script1.id() != -1 && script2.id() != -1);
   return script1.id() < script2.id();
 }
 
 }  // namespace extensions