Keep prototype maps in dictionary mode until ICs see them

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index 287f6bb2e1db6c644564602ef3f551d33a8bb877..168fe71ac458f24ea9f8b35f50ed2522737e68c4 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -2170,6 +2170,8 @@ class JSObject: public JSReceiver {
   static void OptimizeAsPrototype(Handle<JSObject> object,
                                   PrototypeOptimizationMode mode);
   static void ReoptimizeIfPrototype(Handle<JSObject> object);
+  static void MakePrototypesFast(Handle<Object> receiver,
+                                 WhereToStart where_to_start, Isolate* isolate);
   static void LazyRegisterPrototypeUser(Handle<Map> user, Isolate* isolate);
   static void UpdatePrototypeUserRegistration(Handle<Map> old_map,
                                               Handle<Map> new_map,
@@ -5747,6 +5749,9 @@ class Map: public HeapObject {
       Handle<JSObject> prototype, Isolate* isolate);
   static Handle<PrototypeInfo> GetOrCreatePrototypeInfo(
       Handle<Map> prototype_map, Isolate* isolate);
+  inline bool should_be_fast_prototype_map() const;
+  static void SetShouldBeFastPrototypeMap(Handle<Map> map, bool value,
+                                          Isolate* isolate);
 
   // [prototype chain validity cell]: Associated with a prototype object,
   // stored in that object's map's PrototypeInfo, indicates that prototype
@@ -6314,6 +6319,11 @@ class PrototypeInfo : public Struct {
   // given receiver embed the currently valid cell for that receiver's prototype
   // during their compilation and check it on execution.
   DECL_ACCESSORS(validity_cell, Object)
+  // [bit_field]
+  inline int bit_field() const;
+  inline void set_bit_field(int bit_field);
+
+  DECL_BOOLEAN_ACCESSORS(should_be_fast_map)
 
   DECLARE_CAST(PrototypeInfo)
 
@@ -6324,8 +6334,11 @@ class PrototypeInfo : public Struct {
   static const int kPrototypeUsersOffset = HeapObject::kHeaderSize;
   static const int kRegistrySlotOffset = kPrototypeUsersOffset + kPointerSize;
   static const int kValidityCellOffset = kRegistrySlotOffset + kPointerSize;
-  static const int kConstructorNameOffset = kValidityCellOffset + kPointerSize;
-  static const int kSize = kConstructorNameOffset + kPointerSize;
+  static const int kBitFieldOffset = kValidityCellOffset + kPointerSize;
+  static const int kSize = kBitFieldOffset + kPointerSize;
+
+  // Bit field usage.
+  static const int kShouldBeFastBit = 0;
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(PrototypeInfo);