Use a dictionary-mode code cache on the map rather than a dual system.

src/ic/x64/stub-cache-x64.cc

Index: src/ic/x64/stub-cache-x64.cc
diff --git a/src/ic/x64/stub-cache-x64.cc b/src/ic/x64/stub-cache-x64.cc
index 9a9dfe9f4bc34e76b138b2d8249356182411b4dc..e009e983e7ece08e3006c97f30cc85b27df800ec 100644
--- a/src/ic/x64/stub-cache-x64.cc
+++ b/src/ic/x64/stub-cache-x64.cc
@@ -93,9 +93,6 @@ void StubCache::GenerateProbe(MacroAssembler* masm, Code::Kind ic_kind,
   // entry size being 3 * kPointerSize.
   DCHECK(sizeof(Entry) == 3 * kPointerSize);
 
-  // Make sure the flags do not name a specific type.
-  DCHECK(Code::ExtractTypeFromFlags(flags) == 0);
-
   // Make sure that there are no register conflicts.
   DCHECK(!scratch.is(receiver));
   DCHECK(!scratch.is(name));