Don't include source maps in release mode.

sdk/lib/_internal/pub/lib/src/dart.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.
 
 /// A library for compiling Dart code and manipulating analyzer parse trees.
 library pub.dart;
 
 import 'dart:async';
 import 'dart:isolate';
 
@@ skipping 44 matching lines @@
     bool checked: false,
     bool minify: true,
     bool verbose: false,
     Map<String, String> environment,
     String packageRoot,
     bool analyzeAll: false,
     bool suppressWarnings: false,
     bool suppressHints: false,
     bool suppressPackageWarnings: true,
     bool terse: false,
+    bool includeSourceMapUrls: false,
     bool toDart: false}) {
   return syncFuture(() {
     var options = <String>['--categories=Client,Server'];
     if (checked) options.add('--checked');
     if (minify) options.add('--minify');
     if (verbose) options.add('--verbose');
     if (analyzeAll) options.add('--analyze-all');
     if (suppressWarnings) options.add('--suppress-warnings');
     if (suppressHints) options.add('--suppress-hints');
     if (!suppressPackageWarnings) options.add('--show-package-warnings');
     if (terse) options.add('--terse');
     if (toDart) options.add('--output-type=dart');
 
     // Add the source map URLs.
-    var sourceUrl = path.toUri(entrypoint);
-    options.add("--out=$sourceUrl.js");
-    options.add("--source-map=$sourceUrl.js.map");
+    if (includeSourceMapUrls) {
+      var sourceUrl = path.toUri(entrypoint);
+      options.add("--out=$sourceUrl.js");
+      options.add("--source-map=$sourceUrl.js.map");
+    }
 
     if (environment == null) environment = {};
     if (commandLineOptions != null) options.addAll(commandLineOptions);
 
     if (packageRoot == null) {
       packageRoot = path.join(path.dirname(entrypoint), 'packages');
     }
 
     return Chain.track(compiler.compile(
         path.toUri(entrypoint),
@@ skipping 109 matching lines @@
     if (stack == null && error is Error) stack = error.stackTrace;
     return {
       'type': error.runtimeType.toString(),
       'message': getErrorMessage(error),
       'stack': stack == null ? null : new Chain.forTrace(stack).toString()
     };
   }
 
   String toString() => "$message\n$stackTrace";
 }