Proof of concept implementation of context based history filtering.

components/history/core/browser/history_types.h

Index: components/history/core/browser/history_types.h
diff --git a/components/history/core/browser/history_types.h b/components/history/core/browser/history_types.h
index a49ee300a01edb365c43b488bdf374619295e71c..771f4004bc13c524ec4e5652ce1d9f00792f185d 100644
--- a/components/history/core/browser/history_types.h
+++ b/components/history/core/browser/history_types.h
@@ -97,7 +97,7 @@ class VisitRow {
   // This includes both active and inactive time as long as
   // the visit was present.
   base::TimeDelta visit_duration;
-
+  HistoryContext context;
   // Compares two visits based on dates, for sorting.
   bool operator<(const VisitRow& other) {
     return visit_time < other.visit_time;
@@ -241,7 +241,7 @@ struct QueryOptions {
   // time range.
   base::Time begin_time;
   base::Time end_time;
-
+  HistoryContext context;
   // Sets the query time to the last |days_ago| days to the present time.
   void SetRecentDayRange(int days_ago);