Replace uses of hash_map in //base

base/id_map_unittest.cc

Index: base/id_map_unittest.cc
diff --git a/base/id_map_unittest.cc b/base/id_map_unittest.cc
index 42949bb5b95c25ba3e91e5fd801693e0fe359ba6..15f0c24b73ad4397ef83d6f88eb9575ae2b57af1 100644
--- a/base/id_map_unittest.cc
+++ b/base/id_map_unittest.cc
@@ -106,7 +106,7 @@ TEST(IDMapTest, IteratorRemainsValidWhenRemovingOtherElements) {
   for (int i = 0; i < kCount; i++)
     map.Add(&obj[i]);
 
-  // IDMap uses a hash_map, which has no predictable iteration order.
+  // IDMap has no predictable iteration order.
   int32_t ids_in_iteration_order[kCount];
   const TestObject* objs_in_iteration_order[kCount];
   int counter = 0;
@@ -216,7 +216,7 @@ TEST(IDMapTest, IteratorRemainsValidWhenClearing) {
   for (int i = 0; i < kCount; i++)
     map.Add(&obj[i]);
 
-  // IDMap uses a hash_map, which has no predictable iteration order.
+  // IDMap has no predictable iteration order.
   int32_t ids_in_iteration_order[kCount];
   const TestObject* objs_in_iteration_order[kCount];
   int counter = 0;