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 9644ba2e92e2dc5d54413abbe35cd57160b9e11d..7f94ba02745562858abe19f8dc0bbe0148ba3074 100644
--- a/dart/sdk/lib/_internal/compiler/implementation/js_backend/backend.dart
+++ b/dart/sdk/lib/_internal/compiler/implementation/js_backend/backend.dart
@@ -811,6 +811,11 @@ 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);
@@ -991,6 +996,7 @@ 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;
@@ -1048,6 +1054,7 @@ 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
@@ -1736,6 +1743,8 @@ 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);
   }