Implement the compiler API and use it in frog_leg.dart.

dart/frog/leg/api.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #library('leg_api');
-#import('dart:uri');
+
+#import('../../lib/uri/uri.dart');
+#import('apiimpl.dart');
 
 // Unless explicitly allowed, passing null for any argument to the
 // methods of library will result in a NullPointerException being
 // thrown.
 
 /**
  * Returns the source corresponding to [uri]. If no such source exists
  * or if an error occur while fetching it, this method must throw an
  * exception.
  */
@@ skipping 10 matching lines @@
  * from returning null.
  */
 typedef void DiagnosticHandler(Uri uri, int begin, int end,
                                String message, bool fatal);
 
 /**
  * Returns [script] compiled to JavaScript. If the compilation fails,
  * null is returned and [handler] will have been invoked at least once
  * with [:fatal == true:].
  */
-Future<String> compile(Uri script, Uri libraryRoot,
-                       ReadUriFromString provider, DiagnosticHandler handler);
-// TODO(ahe): Document libraryRoot argument.
+Future<String> compile(Uri script,
+                       Uri libraryRoot,
+                       ReadUriFromString provider,
+                       DiagnosticHandler handler) {
+  Compiler compiler = new Compiler(provider, handler, libraryRoot);
+  compiler.run(script);
+  String code = compiler.assembledCode;
+  Completer<String> completer = new Completer<String>();
+  completer.complete(code);
+  return completer.future;
+}