Use a better hash function in IdentityMap.

src/identity-map.h

Index: src/identity-map.h
diff --git a/src/identity-map.h b/src/identity-map.h
index de0aef5bd4524202f80fbed324c254528fd7dda1..ad2a2607693d34724c7417535eb5939088303f3f 100644
--- a/src/identity-map.h
+++ b/src/identity-map.h
@@ -5,6 +5,7 @@
 #ifndef V8_IDENTITY_MAP_H_
 #define V8_IDENTITY_MAP_H_
 
+#include "src/base/functional.h"
 #include "src/handles.h"
 
 namespace v8 {
@@ -48,6 +49,7 @@ class IdentityMapBase {
   RawEntry Insert(Object* key);
   int Hash(Object* address);
 
+  base::hash<uintptr_t> hasher_;
   Heap* heap_;
   Zone* zone_;
   int gc_counter_;