Remove uses of base::hash_map from //chrome

chrome/browser/sync_file_system/subtree_set.h

Index: chrome/browser/sync_file_system/subtree_set.h
diff --git a/chrome/browser/sync_file_system/subtree_set.h b/chrome/browser/sync_file_system/subtree_set.h
index 40e232b2a7eb033478df4e1a3d223a1822719aff..190165fd7fec291d06c2ebb45ec94e5efc555112 100644
--- a/chrome/browser/sync_file_system/subtree_set.h
+++ b/chrome/browser/sync_file_system/subtree_set.h
@@ -7,6 +7,8 @@
 
 #include <stddef.h>
 
+#include <unordered_map>
+
 #include "base/containers/hash_tables.h"
 #include "base/files/file_path.h"
 
@@ -49,7 +51,7 @@ class SubtreeSet {
   };
 
   typedef base::FilePath::StringType StringType;
-  typedef base::hash_map<StringType, Node> Subtrees;
+  typedef std::unordered_map<StringType, Node> Subtrees;
 
   // Contains the root of subtrees and all upward node to root.
   // Each subtree root has |contained_as_subtree_root| flag true.