There are only 2 language modes, not 3

src/objects.cc

Index: src/objects.cc
diff --git a/src/objects.cc b/src/objects.cc
index d1dd44c139d8ad8100b5e859ef9307d7e30fd76d..7a8664cfd6cbdfb4b5f854b4c5f6bbc6dddfd3f4 100644
--- a/src/objects.cc
+++ b/src/objects.cc
@@ -9163,22 +9163,15 @@ Handle<Map> Map::AsLanguageMode(Handle<Map> initial_map,
   // using |strict_function_transition_symbol| as a key.
   if (language_mode == SLOPPY) return initial_map;
   Isolate* isolate = initial_map->GetIsolate();
-  Factory* factory = isolate->factory();
-  Handle<Symbol> transition_symbol;
 
   int map_index = Context::FunctionMapIndex(language_mode, kind);
   Handle<Map> function_map(
       Map::cast(isolate->native_context()->get(map_index)));
 
-  STATIC_ASSERT(LANGUAGE_END == 3);
-  switch (language_mode) {
-    case STRICT:
-      transition_symbol = factory->strict_function_transition_symbol();
-      break;
-    default:
-      UNREACHABLE();
-      break;
-  }
+  STATIC_ASSERT(LANGUAGE_END == 2);
+  DCHECK_EQ(STRICT, language_mode);
+  Handle<Symbol> transition_symbol =
+      isolate->factory()->strict_function_transition_symbol();
   Map* maybe_transition =
       TransitionArray::SearchSpecial(*initial_map, *transition_symbol);
   if (maybe_transition != NULL) {
@@ -16020,7 +16013,7 @@ class StringSharedKey : public HashTableKey {
       // collection.
       Script* script(Script::cast(shared->script()));
       hash ^= String::cast(script->source())->Hash();
-      STATIC_ASSERT(LANGUAGE_END == 3);
+      STATIC_ASSERT(LANGUAGE_END == 2);
       if (is_strict(language_mode)) hash ^= 0x8000;
       hash += scope_position;
     }