Retain elements a finer granularity than library.

dart/sdk/lib/_internal/compiler/implementation/apiimpl.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_apiimpl;
 
 import 'dart:async';
 
 import '../compiler.dart' as api;
 import 'dart2jslib.dart' as leg;
@@ skipping 40 matching lines @@
             strips: extractCsvOption(options, '--force-strip='),
             enableConcreteTypeInference:
                 hasOption(options, '--enable-concrete-type-inference'),
             disableTypeInferenceFlag:
                 hasOption(options, '--disable-type-inference'),
             preserveComments: hasOption(options, '--preserve-comments'),
             verbose: hasOption(options, '--verbose'),
             sourceMapUri: extractSourceMapUri(options),
             globalJsName: extractStringOption(
                 options, '--global-js-name=', r'$'),
+            terseDiagnostics: hasOption(options, '--terse'),
             buildId: extractStringOption(
                 options, '--build-id=',
                 "build number could not be determined")) {
     if (!libraryRoot.path.endsWith("/")) {
       throw new ArgumentError("libraryRoot must end with a /");
     }
     if (packageRoot != null && !packageRoot.path.endsWith("/")) {
       throw new ArgumentError("packageRoot must end with a /");
     }
   }
@@ skipping 225 matching lines @@
       handler(translateUri(span.uri, null), span.begin, span.end,
               message, kind);
     }
   }
 
   bool get isMockCompilation {
     return mockableLibraryUsed
       && (options.indexOf('--allow-mock-compilation') != -1);
   }
 }