alternate ntp: implement Show/HideBars API to reduce jank when showing/hiding bars

chrome/common/search_types.h

 // Copyright (c) 2012 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_COMMON_SEARCH_TYPES_H_
 #define CHROME_COMMON_SEARCH_TYPES_H_
 
 namespace chrome {
 namespace search {
 
@@ skipping 32 matching lines @@
 
   Mode(Type in_mode, Origin in_origin)
       : mode(in_mode),
         origin(in_origin) {
   }
 
   bool operator==(const Mode& rhs) const {
     return mode == rhs.mode && origin == rhs.origin;
   }
 
+  bool operator!=(const Mode& rhs) const {
+    return !(*this == rhs);
+  }
+
   bool is_default() const {
     return mode == MODE_DEFAULT;
   }
 
   bool is_ntp() const {
     return mode == MODE_NTP;
   }
 
   bool is_search() const {
     return mode == MODE_SEARCH_SUGGESTIONS || mode == MODE_SEARCH_RESULTS;
@@ skipping 20 matching lines @@
   }
 
   Type mode;
   Origin origin;
 };
 
 }  // namespace search
 }  // namespace chrome
 
 #endif  // CHROME_COMMON_SEARCH_TYPES_H_