Support passing CSP configuration to the dart2js transformer.

sdk/lib/_internal/pub/lib/src/barback/dart2js_transformer.dart

Index: sdk/lib/_internal/pub/lib/src/barback/dart2js_transformer.dart
diff --git a/sdk/lib/_internal/pub/lib/src/barback/dart2js_transformer.dart b/sdk/lib/_internal/pub/lib/src/barback/dart2js_transformer.dart
index 6f21c8de5360dab40b6749273d90590a73227703..814dbbeb3c3cf10e0cea555e9cb5b8734436f414 100644
--- a/sdk/lib/_internal/pub/lib/src/barback/dart2js_transformer.dart
+++ b/sdk/lib/_internal/pub/lib/src/barback/dart2js_transformer.dart
@@ -24,7 +24,7 @@ import 'asset_environment.dart';
 
 /// The set of all valid configuration options for this transformer.
 final _validOptions = new Set<String>.from([
-  'commandLineOptions', 'checked', 'minify', 'verbose', 'environment',
+  'commandLineOptions', 'checked', 'csp', 'minify', 'verbose', 'environment',
   'analyzeAll', 'suppressWarnings', 'suppressHints', 'suppressPackageWarnings',
   'terse'
 ]);
@@ -135,6 +135,7 @@ class Dart2JSTransformer extends Transformer implements LazyTransformer {
     return Chain.track(dart.compile(
         entrypoint, provider,
         commandLineOptions: _configCommandLineOptions,
+        csp: _configBool('csp'),
         checked: _configBool('checked'),
         minify: _configBool(
             'minify', defaultsTo: _settings.mode == BarbackMode.RELEASE),