diff --git a/src/runtime/runtime-scopes.cc b/src/runtime/runtime-scopes.cc
index de0d66a..68df582 100644
--- a/src/runtime/runtime-scopes.cc
+++ b/src/runtime/runtime-scopes.cc
@@ -44,8 +44,7 @@
   }
 
   // Do the lookup own properties only, see ES5 erratum.
-  LookupIterator it(global, name, global,
-                    LookupIterator::HIDDEN_SKIP_INTERCEPTOR);
+  LookupIterator it(global, name, global, LookupIterator::OWN_SKIP_INTERCEPTOR);
   Maybe<PropertyAttributes> maybe = JSReceiver::GetPropertyAttributes(&it);
   if (!maybe.IsJust()) return isolate->heap()->exception();
 
@@ -182,8 +181,7 @@
   Handle<JSGlobalObject> global = isolate->global_object();
 
   // Lookup the property as own on the global object.
-  LookupIterator it(global, name, global,
-                    LookupIterator::HIDDEN_SKIP_INTERCEPTOR);
+  LookupIterator it(global, name, global, LookupIterator::OWN_SKIP_INTERCEPTOR);
   Maybe<PropertyAttributes> maybe = JSReceiver::GetPropertyAttributes(&it);
   DCHECK(maybe.IsJust());
   PropertyAttributes old_attributes = maybe.FromJust();
@@ -237,10 +235,7 @@
     // Check for a conflict with a lexically scoped variable
     context_arg->Lookup(name, LEXICAL_TEST, &index, &attributes,
                         &binding_flags);
-    if (attributes != ABSENT &&
-        (binding_flags == MUTABLE_CHECK_INITIALIZED ||
-         binding_flags == IMMUTABLE_CHECK_INITIALIZED ||
-         binding_flags == IMMUTABLE_CHECK_INITIALIZED_HARMONY)) {
+    if (attributes != ABSENT && binding_flags == BINDING_CHECK_INITIALIZED) {
       return ThrowRedeclarationError(isolate, name);
     }
     attr = static_cast<PropertyAttributes>(attr & ~EVAL_DECLARED);
@@ -339,86 +334,6 @@
 }
 
 
-RUNTIME_FUNCTION(Runtime_InitializeLegacyConstLookupSlot) {
-  HandleScope scope(isolate);
-  DCHECK(args.length() == 3);
-
-  CONVERT_ARG_HANDLE_CHECKED(Object, value, 0);
-  DCHECK(!value->IsTheHole());
-  // Initializations are always done in a function or native context.
-  CONVERT_ARG_HANDLE_CHECKED(Context, context_arg, 1);
-  Handle<Context> context(context_arg->declaration_context());
-  CONVERT_ARG_HANDLE_CHECKED(String, name, 2);
-
-  int index;
-  PropertyAttributes attributes;
-  ContextLookupFlags flags = DONT_FOLLOW_CHAINS;
-  BindingFlags binding_flags;
-  Handle<Object> holder =
-      context->Lookup(name, flags, &index, &attributes, &binding_flags);
-  if (holder.is_null()) {
-    // In case of JSProxy, an exception might have been thrown.
-    if (isolate->has_pending_exception()) return isolate->heap()->exception();
-  }
-
-  if (index != Context::kNotFound) {
-    DCHECK(holder->IsContext());
-    // Property was found in a context.  Perform the assignment if the constant
-    // was uninitialized.
-    Handle<Context> context = Handle<Context>::cast(holder);
-    DCHECK((attributes & READ_ONLY) != 0);
-    if (context->get(index)->IsTheHole()) context->set(index, *value);
-    return *value;
-  }
-
-  PropertyAttributes attr =
-      static_cast<PropertyAttributes>(DONT_DELETE | READ_ONLY);
-
-  // Strict mode handling not needed (legacy const is disallowed in strict
-  // mode).
-
-  // The declared const was configurable, and may have been deleted in the
-  // meanwhile. If so, re-introduce the variable in the context extension.
-  if (attributes == ABSENT) {
-    Handle<Context> declaration_context(context_arg->declaration_context());
-    if (declaration_context->IsScriptContext()) {
-      holder = handle(declaration_context->global_object(), isolate);
-    } else {
-      holder = handle(declaration_context->extension_object(), isolate);
-      DCHECK(!holder.is_null());
-    }
-    CHECK(holder->IsJSObject());
-  } else {
-    // For JSContextExtensionObjects, the initializer can be run multiple times
-    // if in a for loop: for (var i = 0; i < 2; i++) { const x = i; }. Only the
-    // first assignment should go through. For JSGlobalObjects, additionally any
-    // code can run in between that modifies the declared property.
-    DCHECK(holder->IsJSGlobalObject() || holder->IsJSContextExtensionObject());
-
-    LookupIterator it(holder, name, Handle<JSReceiver>::cast(holder),
-                      LookupIterator::HIDDEN_SKIP_INTERCEPTOR);
-    Maybe<PropertyAttributes> maybe = JSReceiver::GetPropertyAttributes(&it);
-    if (!maybe.IsJust()) return isolate->heap()->exception();
-    PropertyAttributes old_attributes = maybe.FromJust();
-
-    // Ignore if we can't reconfigure the value.
-    if ((old_attributes & DONT_DELETE) != 0) {
-      if ((old_attributes & READ_ONLY) != 0 ||
-          it.state() == LookupIterator::ACCESSOR) {
-        return *value;
-      }
-      attr = static_cast<PropertyAttributes>(old_attributes | READ_ONLY);
-    }
-  }
-
-  RETURN_FAILURE_ON_EXCEPTION(
-      isolate, JSObject::SetOwnPropertyIgnoreAttributes(
-                   Handle<JSObject>::cast(holder), name, value, attr));
-
-  return *value;
-}
-
-
 namespace {
 
 // Find the arguments of the JavaScript function invocation that called
@@ -648,7 +563,7 @@
   {
     DisallowHeapAllocation no_gc;
     FixedArray* elements = FixedArray::cast(result->elements());
-    WriteBarrierMode mode = result->GetWriteBarrierMode(no_gc);
+    WriteBarrierMode mode = elements->GetWriteBarrierMode(no_gc);
     for (int i = 0; i < num_elements; i++) {
       elements->set(i, *arguments[i + start_index], mode);
     }
@@ -663,12 +578,6 @@
   CONVERT_ARG_HANDLE_CHECKED(JSFunction, callee, 0);
   Object** parameters = reinterpret_cast<Object**>(args[1]);
   CONVERT_SMI_ARG_CHECKED(argument_count, 2);
-#ifdef DEBUG
-  // This runtime function does not materialize the correct arguments when the
-  // caller has been inlined, better make sure we are not hitting that case.
-  JavaScriptFrameIterator it(isolate);
-  DCHECK(!it.frame()->HasInlinedFrames());
-#endif  // DEBUG
   ParameterArguments argument_getter(parameters);
   return *NewSloppyArguments(isolate, callee, argument_getter, argument_count);
 }
@@ -711,7 +620,7 @@
 
     if (IsLexicalVariableMode(mode)) {
       LookupIterator it(global_object, name, global_object,
-                        LookupIterator::HIDDEN_SKIP_INTERCEPTOR);
+                        LookupIterator::OWN_SKIP_INTERCEPTOR);
       Maybe<PropertyAttributes> maybe = JSReceiver::GetPropertyAttributes(&it);
       if (!maybe.IsJust()) return isolate->heap()->exception();
       if ((maybe.FromJust() & DONT_DELETE) != 0) {
@@ -875,8 +784,7 @@
         case VAR:
         case LET:
         case CONST:
-        case CONST_LEGACY:
-        case IMPORT: {
+        case CONST_LEGACY: {
           PropertyAttributes attr =
               IsImmutableVariableMode(mode) ? FROZEN : SEALED;
           Handle<AccessorInfo> info =
@@ -961,23 +869,14 @@
     Handle<Object> value = handle(Context::cast(*holder)->get(index), isolate);
     // Check for uninitialized bindings.
     switch (flags) {
-      case MUTABLE_CHECK_INITIALIZED:
-      case IMMUTABLE_CHECK_INITIALIZED_HARMONY:
+      case BINDING_CHECK_INITIALIZED:
         if (value->IsTheHole()) {
           THROW_NEW_ERROR(isolate,
                           NewReferenceError(MessageTemplate::kNotDefined, name),
                           Object);
         }
       // FALLTHROUGH
-      case IMMUTABLE_CHECK_INITIALIZED:
-        if (value->IsTheHole()) {
-          DCHECK(attributes & READ_ONLY);
-          value = isolate->factory()->undefined_value();
-        }
-      // FALLTHROUGH
-      case MUTABLE_IS_INITIALIZED:
-      case IMMUTABLE_IS_INITIALIZED:
-      case IMMUTABLE_IS_INITIALIZED_HARMONY:
+      case BINDING_IS_INITIALIZED:
         DCHECK(!value->IsTheHole());
         if (receiver_return) *receiver_return = receiver;
         return value;
@@ -1075,8 +974,7 @@
 
   // The property was found in a context slot.
   if (index != Context::kNotFound) {
-    if ((flags == MUTABLE_CHECK_INITIALIZED ||
-         flags == IMMUTABLE_CHECK_INITIALIZED_HARMONY) &&
+    if (flags == BINDING_CHECK_INITIALIZED &&
         Handle<Context>::cast(holder)->is_the_hole(index)) {
       THROW_NEW_ERROR(isolate,
                       NewReferenceError(MessageTemplate::kNotDefined, name),