Only generate assert in checked mode.

lib/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:uri');
 
 #import('../compiler.dart', prefix: 'api');
 #import('leg.dart', prefix: 'leg');
@@ skipping 10 matching lines @@
   final Uri packageRoot;
   List<String> options;
   bool mockableLibraryUsed = false;
 
   Compiler(this.provider, this.handler, this.libraryRoot, this.packageRoot,
            List<String> options)
     : this.options = options,
       super(
           tracer: new ssa.HTracer(),
           enableTypeAssertions: options.indexOf('--enable-checked-mode') != -1,
+          enableUserAssertions: options.indexOf('--enable-checked-mode') != -1,
           emitJavascript: options.indexOf('--output-type=dart') == -1,
           validateUnparse: options.indexOf('--unparse-validation') !== -1);
 
   elements.LibraryElement scanBuiltinLibrary(String path) {
     Uri uri = libraryRoot.resolve(DART2JS_LIBRARY_MAP[path]);
     elements.LibraryElement library = scanner.loadLibrary(uri, null);
     return library;
   }
 
   void log(message) {
@@ skipping 55 matching lines @@
     } else {
       handler(span.uri, span.begin, span.end, message, fatal);
     }
   }
 
   bool get isMockCompilation() {
     return mockableLibraryUsed
       && (options.indexOf('--allow-mock-compilation') !== -1);
   }
 }