First pass at asynchronous input loading in dart2js.

sdk/lib/_internal/compiler/implementation/dart2js.dart

 // Copyright (c) 2013, 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 dart2js.cmdline;
 
 import 'dart:async';
 import 'dart:io';
 import 'dart:math' as math;
 
@@ skipping 73 matching lines @@
         } else {
           handler.handle(argument);
         }
         continue OUTER;
       }
     }
     throw 'Internal error: "$argument" did not match';
   }
 }
 
-void compile(List<String> argv) {
+Future compile(List<String> argv) {
   bool isWindows = (Platform.operatingSystem == 'windows');
   stackTraceFilePrefix = '$currentDirectory';
   Uri libraryRoot = currentDirectory;
   Uri out = currentDirectory.resolve('out.js');
   Uri sourceMapOut = currentDirectory.resolve('out.js.map');
   Uri packageRoot = null;
   List<String> options = new List<String>();
   bool explicitOut = false;
   bool wantHelp = false;
   bool wantVersion = false;
@@ skipping 276 matching lines @@
       }
       output.closeSync();
       if (isPrimaryOutput) {
         totalCharactersWritten += charactersWritten;
       }
     }
 
     return new EventSinkWrapper(writeStringSync, onDone);
   }
 
-  api.compile(uri, libraryRoot, packageRoot,
+  return api.compile(uri, libraryRoot, packageRoot,
               inputProvider.readStringFromUri, handler,
               options, outputProvider)
-      .then(compilationDone);
+            .then(compilationDone);
 }
 
 class EventSinkWrapper extends EventSink<String> {
   var onAdd, onClose;
 
   EventSinkWrapper(this.onAdd, this.onClose);
 
   void add(String data) => onAdd(data);
 
   void addError(error) => throw error;
@@ skipping 14 matching lines @@
   var file = new File(uriPathToNative(uri.path)).openSync(mode: FileMode.WRITE);
   file.writeStringSync(text);
   file.closeSync();
 }
 
 void fail(String message) {
   print(message);
   exit(1);
 }
 
-void compilerMain(Options options) {
+Future compilerMain(Options options) {
   var root = uriPathToNative("/$LIBRARY_ROOT");
   List<String> argv = ['--library-root=${options.script}$root'];
   argv.addAll(options.arguments);
-  compile(argv);
+  return compile(argv);
 }
 
 void help() {
   // This message should be no longer than 20 lines. The default
   // terminal size normally 80x24. Two lines are used for the prompts
   // before and after running the compiler. Another two lines may be
   // used to print an error message.
   print('''
 Usage: dart2js [options] dartfile
 
@@ skipping 126 matching lines @@
   exit(0);
 }
 
 void helpAndFail(String message) {
   help();
   print('');
   fail(message);
 }
 
 void mainWithErrorHandler(Options options) {
-  try {
-    compilerMain(options);
-  } catch (exception, trace) {
+  compilerMain(options).catchError((exception) {
     try {
       print('Internal error: $exception');
     } catch (ignored) {
       print('Internal error: error while printing exception');
     }
+    
     try {
-      print(trace);
+      var trace = getAttachedStackTrace(exception);
+      if (trace != null) {
+        print(trace);
+      }
     } finally {
       exit(253); // 253 is recognized as a crash by our test scripts.
     }
-  }
+  });
 }
 
 void main() {
   mainWithErrorHandler(new Options());
 }