[serializer] cache ICs only as code stubs with key.

src/snapshot/code-serializer.h

Index: src/snapshot/code-serializer.h
diff --git a/src/snapshot/code-serializer.h b/src/snapshot/code-serializer.h
index b217fff52b84f109a977317331373f0cc8d35ed3..48f3bc525907e81acb8276486d44f920d94b70f9 100644
--- a/src/snapshot/code-serializer.h
+++ b/src/snapshot/code-serializer.h
@@ -45,8 +45,6 @@ class CodeSerializer : public Serializer {
 
   void SerializeBuiltin(int builtin_index, HowToCode how_to_code,
                         WhereToPoint where_to_point);
-  void SerializeIC(Code* ic, HowToCode how_to_code,
-                   WhereToPoint where_to_point);
   void SerializeCodeStub(uint32_t stub_key, HowToCode how_to_code,
                          WhereToPoint where_to_point);
   void SerializeGeneric(HeapObject* heap_object, HowToCode how_to_code,