Cleanup: Remove unneeded forward declarations from various chrome/browser subdirectories.

chrome/browser/autocomplete/autocomplete.h

 // 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.
 
 #ifndef CHROME_BROWSER_AUTOCOMPLETE_AUTOCOMPLETE_H_
 #define CHROME_BROWSER_AUTOCOMPLETE_AUTOCOMPLETE_H_
 #pragma once
 
 #include <map>
 #include <string>
@@ skipping 156 matching lines @@
 // *~: Partial matches get a score on a sliding scale from about 575-1125 based
 //     on how many times the URL for the Extension App has been typed and how
 //     many of the letters match.
 
 class AutocompleteController;
 class AutocompleteControllerDelegate;
 class AutocompleteInput;
 struct AutocompleteMatch;
 class AutocompleteProvider;
 class AutocompleteResult;
-class HistoryContentsProvider;
 class KeywordProvider;
 class Profile;
 class SearchProvider;
 class TemplateURL;
 
 typedef std::vector<AutocompleteMatch> ACMatches;
 typedef std::vector<AutocompleteProvider*> ACProviders;
 
 // AutocompleteInput ----------------------------------------------------------
 
@@ skipping 564 matching lines @@
   AutocompleteInput::Type input_type;
   // Selected index (if selected) or -1 (AutocompletePopupModel::kNoMatch).
   size_t selected_index;
   // Inline autocompleted length (if displayed).
   size_t inline_autocompleted_length;
   // Result set.
   const AutocompleteResult& result;
 };
 
 #endif  // CHROME_BROWSER_AUTOCOMPLETE_AUTOCOMPLETE_H_