Don't include source maps in release mode.

sdk/lib/_internal/pub/lib/src/dart.dart

Index: sdk/lib/_internal/pub/lib/src/dart.dart
diff --git a/sdk/lib/_internal/pub/lib/src/dart.dart b/sdk/lib/_internal/pub/lib/src/dart.dart
index 7da4b172def7809d4e25f9a772d3792f2b7db6a6..530c798c3b4ab9b159a6900534b729ffbdc88f14 100644
--- a/sdk/lib/_internal/pub/lib/src/dart.dart
+++ b/sdk/lib/_internal/pub/lib/src/dart.dart
@@ -62,6 +62,7 @@ Future compile(String entrypoint, CompilerProvider provider, {
     bool suppressHints: false,
     bool suppressPackageWarnings: true,
     bool terse: false,
+    bool includeSourceMapUrls: false,
     bool toDart: false}) {
   return syncFuture(() {
     var options = <String>['--categories=Client,Server'];
@@ -76,9 +77,11 @@ Future compile(String entrypoint, CompilerProvider provider, {
     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);