Proof of concept implementation of context based history filtering.

components/history/core/browser/url_database.h

 // Copyright 2014 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 COMPONENTS_HISTORY_CORE_BROWSER_URL_DATABASE_H_
 #define COMPONENTS_HISTORY_CORE_BROWSER_URL_DATABASE_H_
 
 #include "base/basictypes.h"
 #include "components/history/core/browser/keyword_id.h"
 #include "components/history/core/browser/url_row.h"
@@ skipping 283 matching lines @@
 
 // The fields and order expected by FillURLRow(). ID is guaranteed to be first
 // so that DISTINCT can be prepended to get distinct URLs.
 //
 // This is available BOTH as a macro and a static string (kURLRowFields). Use
 // the macro if you want to put this in the middle of an otherwise constant
 // string, it will save time doing string appends. If you have to build a SQL
 // string dynamically anyway, use the constant, it will save space.
 #define HISTORY_URL_ROW_FIELDS \
     " urls.id, urls.url, urls.title, urls.visit_count, urls.typed_count, " \
-    "urls.last_visit_time, urls.hidden "
+    "urls.last_visit_time, urls.context, urls.hidden "
 
 // Constants which specify, when considered altogether, 'significant'
 // history items. These are used to filter out insignificant items
 // for consideration as autocomplete candidates.
 extern const int kLowQualityMatchTypedLimit;
 extern const int kLowQualityMatchVisitLimit;
 extern const int kLowQualityMatchAgeLimitInDays;
 
 // Returns the date threshold for considering an history item as significant.
 base::Time AutocompleteAgeThreshold();
 
 // Return true if |row| qualifies as an autocomplete candidate. If |time_cache|
 // is_null() then this function determines a new time threshold each time it is
 // called. Since getting system time can be costly (such as for cases where
 // this function will be called in a loop over many history items), you can
 // provide a non-null |time_cache| by simply initializing |time_cache| with
 // AutocompleteAgeThreshold() (or any other desired time in the past).
 bool RowQualifiesAsSignificant(const URLRow& row, const base::Time& threshold);
 
 }  // namespace history
 
 #endif  // COMPONENTS_HISTORY_CORE_BROWSER_URL_DATABASE_H_