Introduce OpenWorld.

pkg/compiler/lib/src/ssa/builder.dart

Index: pkg/compiler/lib/src/ssa/builder.dart
diff --git a/pkg/compiler/lib/src/ssa/builder.dart b/pkg/compiler/lib/src/ssa/builder.dart
index 0269ab2ce67abee3aef9a2799da043cffaf9c87c..36b9ed23756fae0afdadbdd8f2de00469af15c7c 100644
--- a/pkg/compiler/lib/src/ssa/builder.dart
+++ b/pkg/compiler/lib/src/ssa/builder.dart
@@ -554,7 +554,7 @@ class SsaBuilder extends ast.Visitor
    */
   List<HInstruction> completeDynamicSendArgumentsList(Selector selector,
       FunctionElement function, List<HInstruction> providedArguments) {
-    assert(selector.applies(function, compiler.closedWorld));
+    assert(selector.applies(function, backend));
     FunctionSignature signature = function.functionSignature;
     List<HInstruction> compiledArguments = new List<HInstruction>(
         signature.parameterCount + 1); // Plus one for receiver.
@@ -648,7 +648,7 @@ class SsaBuilder extends ast.Visitor
               element.isGenerativeConstructorBody,
           message: "Missing selector for inlining of $element."));
       if (selector != null) {
-        if (!selector.applies(function, compiler.closedWorld)) return false;
+        if (!selector.applies(function, backend)) return false;
         if (mask != null &&
             !mask.canHit(function, selector, compiler.closedWorld)) {
           return false;
@@ -3687,7 +3687,7 @@ class SsaBuilder extends ast.Visitor
     // calling [makeStaticArgumentList].
     Selector selector = elements.getSelector(node);
     assert(invariant(
-        node, selector.applies(function.implementation, compiler.closedWorld),
+        node, selector.applies(function.implementation, backend),
         message: "$selector does not apply to ${function.implementation}"));
     List<HInstruction> inputs = makeStaticArgumentList(
         selector.callStructure, node.arguments, function.implementation);
@@ -4943,7 +4943,7 @@ class SsaBuilder extends ast.Visitor
     void generateSuperSendSet() {
       Selector setterSelector = elements.getSelector(node);
       if (Elements.isUnresolved(element) ||
-          !setterSelector.applies(element, compiler.closedWorld)) {
+          !setterSelector.applies(element, compiler.backend)) {
         generateSuperNoSuchMethodSend(node, setterSelector, setterInputs);
         pop();
       } else {