Change HistoryInfoMap to use unordered_map.

components/omnibox/browser/in_memory_url_index_types.h

Index: components/omnibox/browser/in_memory_url_index_types.h
diff --git a/components/omnibox/browser/in_memory_url_index_types.h b/components/omnibox/browser/in_memory_url_index_types.h
index 089559c44557caa604754fc7d8454c8007f4f2fb..f35fd9e0bbec21aaf92f514340c9a0143bea4674 100644
--- a/components/omnibox/browser/in_memory_url_index_types.h
+++ b/components/omnibox/browser/in_memory_url_index_types.h
@@ -9,6 +9,7 @@
 #include <set>
 #include <vector>
 
+#include "base/containers/hash_tables.h"
 #include "base/strings/string16.h"
 #include "components/history/core/browser/history_types.h"
 #include "url/gurl.h"
@@ -153,7 +154,7 @@ struct HistoryInfoMapValue {
 };
 
 // A map from history_id to the history's URL and title.
-typedef std::map<HistoryID, HistoryInfoMapValue> HistoryInfoMap;
+typedef base::hash_map<HistoryID, HistoryInfoMapValue> HistoryInfoMap;
 
 // A map from history_id to URL and page title word start metrics.
 struct RowWordStarts {