Generate tear-off closures dynamically.

dart/sdk/lib/_internal/compiler/implementation/js_backend/backend.dart

Index: dart/sdk/lib/_internal/compiler/implementation/js_backend/backend.dart
diff --git a/dart/sdk/lib/_internal/compiler/implementation/js_backend/backend.dart b/dart/sdk/lib/_internal/compiler/implementation/js_backend/backend.dart
index 7627c616995c244e97ff9de83a03247cfd232386..09093d0b68f3c4b9c08068c85f8ff51683ba536a 100644
--- a/dart/sdk/lib/_internal/compiler/implementation/js_backend/backend.dart
+++ b/dart/sdk/lib/_internal/compiler/implementation/js_backend/backend.dart
@@ -800,6 +800,11 @@ class JavaScriptBackend extends Backend {
         enqueueClass(enqueuer, jsPlainJavaScriptObjectClass, elements);
       }
     }
+    if (cls == compiler.closureClass) {
+      enqueue(enqueuer,
+              compiler.findHelper('closureFromTearOff'),
+              elements);
+    }
     ClassElement result = null;
     if (cls == compiler.stringClass || cls == jsStringClass) {
       addInterceptors(jsStringClass, enqueuer, elements);
@@ -978,6 +983,7 @@ class JavaScriptBackend extends Backend {
   }
 
   void registerIsCheck(DartType type, Enqueuer world, TreeElements elements) {
+    enqueueInResolution(getThrowRuntimeError(), elements);
     type = type.unalias(compiler);
     enqueueClass(world, compiler.boolClass, elements);
     bool inCheckedMode = compiler.enableTypeAssertions;
@@ -1035,6 +1041,7 @@ class JavaScriptBackend extends Backend {
   }
 
   void registerAsCheck(DartType type, Enqueuer world, TreeElements elements) {
+    enqueueInResolution(getThrowRuntimeError(), elements);
     type = type.unalias(compiler);
     if (!world.isResolutionQueue) {
       // All helpers are added to resolution queue in enqueueHelpers. These
@@ -1712,6 +1719,8 @@ class JavaScriptBackend extends Backend {
    * system.
    */
   bool isAccessibleByReflection(Element element) {
+    // TODO(ahe): This isn't sufficient: simply importing dart:mirrors
+    // causes hasInsufficientMirrorsUsed to become true.
     if (hasInsufficientMirrorsUsed) return true;
     return isNeededForReflection(element);
   }