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

src/heap/heap.h

Index: src/heap/heap.h
diff --git a/src/heap/heap.h b/src/heap/heap.h
index f6b49a33a7451583952fdcf0d503b4383cd5aed8..79723e4b89fd080577e9664485422138cf78f4f1 100644
--- a/src/heap/heap.h
+++ b/src/heap/heap.h
@@ -163,7 +163,6 @@ using v8::MemoryPressureLevel;
   V(JSObject, message_listeners, MessageListeners)                             \
   V(UnseededNumberDictionary, code_stubs, CodeStubs)                           \
   V(UnseededNumberDictionary, non_monomorphic_cache, NonMonomorphicCache)      \
-  V(PolymorphicCodeCache, polymorphic_code_cache, PolymorphicCodeCache)        \
   V(Code, js_entry_code, JsEntryCode)                                          \
   V(Code, js_construct_entry_code, JsConstructEntryCode)                       \
   V(FixedArray, natives_source_cache, NativesSourceCache)                      \