Move InMemoryURLIndex into chrome/browser/autocomplete

chrome/browser/autocomplete/in_memory_url_index_cache.proto

 // Copyright (c) 2011 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.
 //
 // InMemoryURLIndex caching protocol buffers.
 //
 // At certain times during browser operation, the indexes from the
 // InMemoryURLIndex are written to a disk-based cache using the
 // following protobuf description.
 
@@ skipping 83 matching lines @@
   optional int32 version = 2;
   required int32 history_item_count = 3;
 
   optional WordListItem word_list = 4;
   optional WordMapItem word_map = 5;
   optional CharWordMapItem char_word_map = 6;
   optional WordIDHistoryMapItem word_id_history_map = 7;
   optional HistoryInfoMapItem history_info_map = 8;
   optional WordStartsMapItem word_starts_map = 9;
 }