Add --no-source-maps flag to dart2js executable

pkg/compiler/lib/src/dart2js.dart

Index: pkg/compiler/lib/src/dart2js.dart
diff --git a/pkg/compiler/lib/src/dart2js.dart b/pkg/compiler/lib/src/dart2js.dart
index 3350684153c007b1313559a875c25e08a7f75579..6f3d3fa2f744a1ee56f55859da5c463361fbb01e 100644
--- a/pkg/compiler/lib/src/dart2js.dart
+++ b/pkg/compiler/lib/src/dart2js.dart
@@ -328,6 +328,7 @@ Future<api.CompilationResult> compile(List<String> argv) {
     new OptionHandler('--package-root=.+|-p.+', setPackageRoot),
     new OptionHandler('--analyze-all', setAnalyzeAll),
     new OptionHandler('--analyze-only', setAnalyzeOnly),
+    new OptionHandler('--no-source-maps', passThrough),
     new OptionHandler('--analyze-signatures-only', setAnalyzeOnly),
     new OptionHandler('--disable-native-live-type-analysis', passThrough),
     new OptionHandler('--categories=.*', setCategories),
@@ -582,6 +583,9 @@ Supported options:
     Disables dynamic generation of code in the generated output. This is
     necessary to satisfy CSP restrictions (see http://www.w3.org/TR/CSP/).
 
+  --no-source-maps
+    Do not generate a source map file.
+
 The following options are only used for compiler development and may
 be removed in a future version: