dart2js: Use an abstract Name class for names in the generated JavaScript ast.

pkg/compiler/lib/src/js_backend/runtime_types.dart

Index: pkg/compiler/lib/src/js_backend/runtime_types.dart
diff --git a/pkg/compiler/lib/src/js_backend/runtime_types.dart b/pkg/compiler/lib/src/js_backend/runtime_types.dart
index 2b13f034dad8861b1e94fa3daf4a0b887d1fd2b4..66be56ad3d5d1d52701f4003028637dca97edb14 100644
--- a/pkg/compiler/lib/src/js_backend/runtime_types.dart
+++ b/pkg/compiler/lib/src/js_backend/runtime_types.dart
@@ -32,7 +32,7 @@ class RuntimeTypes {
 
   JavaScriptBackend get backend => compiler.backend;
 
-  String get getFunctionThatReturnsNullName
+  jsAst.Name get getFunctionThatReturnsNullName
       => backend.namer.internalGlobal('functionThatReturnsNull');
 
   RuntimeTypes(Compiler compiler)
@@ -401,7 +401,7 @@ class RuntimeTypes {
   String getTypeRepresentationForTypeConstant(DartType type) {
     JavaScriptBackend backend = compiler.backend;
     Namer namer = backend.namer;
-    if (type.isDynamic) return namer.runtimeTypeName(null);
+    if (type.isDynamic) return "dynamic";
     String name = namer.uniqueNameForTypeConstantElement(type.element);
     if (!type.element.isClass) return name;
     InterfaceType interface = type;
@@ -541,10 +541,10 @@ class RuntimeTypes {
         getTypeEncoding(type, alwaysGenerateFunction: true);
     if (contextClass != null) {
       JavaScriptBackend backend = compiler.backend;
-      String contextName = backend.namer.className(contextClass);
+      jsAst.Name contextName = backend.namer.className(contextClass);
       return js('function () { return #(#, #, #); }',
           [ backend.emitter.staticFunctionAccess(backend.getComputeSignature()),
-              encoding, this_, js.string(contextName) ]);
+              encoding, this_, js.quoteName(contextName) ]);
     } else {
       return encoding;
     }