Simplify runtime type support.

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

Index: sdk/lib/_internal/compiler/implementation/js_backend/namer.dart
diff --git a/sdk/lib/_internal/compiler/implementation/js_backend/namer.dart b/sdk/lib/_internal/compiler/implementation/js_backend/namer.dart
index 69817be1aaa4dd5b84f84382cdf2a1d0f4366d75..e66b8c0486f36d6ebe16c3f00cfaa0591ec25919 100644
--- a/sdk/lib/_internal/compiler/implementation/js_backend/namer.dart
+++ b/sdk/lib/_internal/compiler/implementation/js_backend/namer.dart
@@ -208,7 +208,7 @@ class Namer {
    * Returns a preferred JS-id for the given top-level or static element.
    * The returned id is guaranteed to be a valid JS-id.
    */
-  String _computeGuess(Element element) {
+  String _computeGuess(Element element, bool allowUnsafeName) {
     assert(!element.isInstanceMember());
     LibraryElement lib = element.getLibrary();
     String name;
@@ -232,8 +232,8 @@ class Namer {
     } else {
       name = element.name.slowToString();
     }
-    // Prefix the name with '$' if it is reserved.
-    return safeName(name);
+    // Prefix the name with '$' if it is reserved and we generate safe names.
+    return allowUnsafeName ? name : safeName(name);
   }
 
   String getBailoutName(Element element) {
@@ -248,7 +248,7 @@ class Namer {
    * For accessing statics consider calling
    * [isolateAccess]/[isolateBailoutAccess] or [isolatePropertyAccess] instead.
    */
-  String getName(Element element) {
+  String getName(Element element, {bool allowUnsafeName: false}) {
     if (element.isInstanceMember()) {
       if (element.kind == ElementKind.GENERATIVE_CONSTRUCTOR_BODY
           || element.kind == ElementKind.FUNCTION) {
@@ -266,12 +266,11 @@ class Namer {
     } else {
       // Use declaration element to ensure invariant on [globals].
       element = element.declaration;
-
       // Dealing with a top-level or static element.
       String cached = globals[element];
       if (cached != null) return cached;
 
-      String guess = _computeGuess(element);
+      String guess = _computeGuess(element, allowUnsafeName);
       ElementKind kind = element.kind;
       if (identical(kind, ElementKind.VARIABLE) ||
           identical(kind, ElementKind.PARAMETER)) {