Add --analyze-signatures-only option to dart2js

sdk/lib/_internal/compiler/implementation/dart2js.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 dart2js;
 
 import 'dart:async';
 import 'dart:collection' show Queue, LinkedHashMap;
 import 'dart:io';
 import 'dart:uri';
@@ skipping 181 matching lines @@
                       (_) => diagnosticHandler.enableColors = true),
     new OptionHandler('--enable[_-]checked[_-]mode|--checked',
                       (_) => passThrough('--enable-checked-mode')),
     new OptionHandler('--enable-concrete-type-inference',
                       (_) => passThrough('--enable-concrete-type-inference')),
     new OptionHandler(r'--help|/\?|/h', (_) => wantHelp = true),
     new OptionHandler('--package-root=.+|-p.+', setPackageRoot),
     new OptionHandler('--disallow-unsafe-eval', passThrough),
     new OptionHandler('--analyze-all', passThrough),
     new OptionHandler('--analyze-only', setAnalyzeOnly),
+    new OptionHandler('--analyze-signatures-only', passThrough),

[ahe, 2013/03/05 14:32:59]

Document option.

[Johnni Winther, 2013/03/05 16:52:49]

Done.

     new OptionHandler('--disable-native-live-type-analysis', passThrough),
     new OptionHandler('--reject-deprecated-language-features', passThrough),
     new OptionHandler('--report-sdk-use-of-deprecated-language-features',
                       passThrough),
     new OptionHandler('--categories=.*', setCategories),
 
     // The following two options must come last.
     new OptionHandler('-.*', (String argument) {
       helpAndFail('Error: Unknown option "$argument".');
     }),
@@ skipping 274 matching lines @@
     } catch (ignored) {
       print('Internal error: error while printing exception');
     }
     try {
       print(trace);
     } finally {
       exit(253); // 253 is recognized as a crash by our test scripts.
     }
   }
 }