Fix all the analysis hints in pub.

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 8c7ff14c0ebc63467759ac3ca87c8bc4f7dbe34a..8bb15277e22c44e87dd5441e644059a2f39ce15a 100644
--- a/sdk/lib/_internal/pub/lib/src/barback/dart2js_transformer.dart
+++ b/sdk/lib/_internal/pub/lib/src/barback/dart2js_transformer.dart
@@ -106,7 +106,7 @@ class Dart2JSTransformer extends Transformer implements LazyTransformer {
 
         var parsed = parseCompilationUnit(code, name: name);
         return dart.isEntrypoint(parsed);
-      } on AnalyzerErrorGroup catch (e) {
+      } on AnalyzerErrorGroup {
         // If we get a parse error, consider the asset primary so we report
         // dart2js's more detailed error message instead.
         return true;
@@ -166,13 +166,15 @@ class Dart2JSTransformer extends Transformer implements LazyTransformer {
 
   /// Parses and returns the "environment" configuration option.
   Map<String, String> get _configEnvironment {
-    if (!_settings.configuration.containsKey('environment')) return null;
+    if (!_settings.configuration.containsKey('environment')) {
+      return _environment.environmentConstants;
+    }
 
     var environment = _settings.configuration['environment'];
     if (environment is Map &&
         environment.keys.every((key) => key is String) &&
         environment.values.every((key) => key is String)) {
-      return environment;
+      return mergeMaps(environment, _environment.environmentConstants);
     }
 
     throw new FormatException('Invalid value for \$dart2js.environment: '