Add support for local variables(including parameters) to cps->js.

pkg/compiler/lib/src/dart_backend/backend_ast_emitter.dart

Index: pkg/compiler/lib/src/dart_backend/backend_ast_emitter.dart
diff --git a/pkg/compiler/lib/src/dart_backend/backend_ast_emitter.dart b/pkg/compiler/lib/src/dart_backend/backend_ast_emitter.dart
index d9d3f3faa16d017e9c67c010e53fa431f80011ad..99c12036abc56e5a4dec79f43c9c4d055c3bb513 100644
--- a/pkg/compiler/lib/src/dart_backend/backend_ast_emitter.dart
+++ b/pkg/compiler/lib/src/dart_backend/backend_ast_emitter.dart
@@ -77,8 +77,7 @@ class ASTEmitter extends tree.Visitor<dynamic, Expression> {
 
     // Declare parameters.
     for (tree.Variable param in definition.parameters) {
-      variableNames[param] = param.element.name;
-      usedVariableNames.add(param.element.name);
+      getVariableName(param);
       declaredVariables.add(param);
     }