Remove all harmony runtime flags which shipped in M51

src/js/runtime.js

Index: src/js/runtime.js
diff --git a/src/js/runtime.js b/src/js/runtime.js
index 23c329651a3e47b5f3ab85ebe20e6b28a96b1cd6..216685fe4f2692eba560e0be9aedd03a919b6c01 100644
--- a/src/js/runtime.js
+++ b/src/js/runtime.js
@@ -16,7 +16,6 @@
 
 %CheckIsBootstrapping();
 
-var FLAG_harmony_species;
 var GlobalArray = global.Array;
 var GlobalBoolean = global.Boolean;
 var GlobalString = global.String;
@@ -30,10 +29,6 @@ utils.Import(function(from) {
   speciesSymbol = from.species_symbol;
 });
 
-utils.ImportFromExperimental(function(from) {
-  FLAG_harmony_species = from.FLAG_harmony_species;
-});
-
 // ----------------------------------------------------------------------------
 
 
@@ -65,35 +60,22 @@ function MinSimple(a, b) {
 
 
 // ES2015 7.3.20
-// For the fallback with --harmony-species off, there are two possible choices:
-//  - "conservative": return defaultConstructor
-//  - "not conservative": return object.constructor
-// This fallback path is only needed in the transition to ES2015, and the
-// choice is made simply to preserve the previous behavior so that we don't
-// have a three-step upgrade: old behavior, unspecified intermediate behavior,
-// and ES2015.
-// In some cases, we were "conservative" (e.g., ArrayBuffer, RegExp), and in
-// other cases we were "not conservative (e.g., TypedArray, Promise).
-function SpeciesConstructor(object, defaultConstructor, conservative) {
-  if (FLAG_harmony_species) {
-    var constructor = object.constructor;
-    if (IS_UNDEFINED(constructor)) {
-      return defaultConstructor;
-    }
-    if (!IS_RECEIVER(constructor)) {
-      throw MakeTypeError(kConstructorNotReceiver);
-    }
-    var species = constructor[speciesSymbol];
-    if (IS_NULL_OR_UNDEFINED(species)) {
-      return defaultConstructor;
-    }
-    if (%IsConstructor(species)) {
-      return species;
-    }
-    throw MakeTypeError(kSpeciesNotConstructor);
-  } else {
-    return conservative ? defaultConstructor : object.constructor;
+function SpeciesConstructor(object, defaultConstructor) {
+  var constructor = object.constructor;
+  if (IS_UNDEFINED(constructor)) {
+    return defaultConstructor;
+  }
+  if (!IS_RECEIVER(constructor)) {
+    throw MakeTypeError(kConstructorNotReceiver);
+  }
+  var species = constructor[speciesSymbol];
+  if (IS_NULL_OR_UNDEFINED(species)) {
+    return defaultConstructor;
+  }
+  if (%IsConstructor(species)) {
+    return species;
   }
+  throw MakeTypeError(kSpeciesNotConstructor);
 }
 
 //----------------------------------------------------------------------------