Proof of concept implementation of context based history filtering.

components/history/core/browser/history_service.h

Index: components/history/core/browser/history_service.h
diff --git a/components/history/core/browser/history_service.h b/components/history/core/browser/history_service.h
index 13d303af824425bdb036a0787633405780ac12ee..d535cfd315a8011f7766482376667ade5e118d87 100644
--- a/components/history/core/browser/history_service.h
+++ b/components/history/core/browser/history_service.h
@@ -196,6 +196,7 @@ class HistoryService : public syncer::SyncableService, public KeyedService {
   // Sets the title for the given page. The page should be in history. If it
   // is not, this operation is ignored.
   void SetPageTitle(const GURL& url, const base::string16& title);
+  void SetPageHistoryContext(const GURL& url, HistoryContext context);
 
   // Updates the history database with a page's ending time stamp information.
   // The page can be identified by the combination of the context id, the