Fix try.

pkg/compiler/samples/jsonify/jsonify.dart

Index: pkg/compiler/samples/jsonify/jsonify.dart
diff --git a/pkg/compiler/samples/jsonify/jsonify.dart b/pkg/compiler/samples/jsonify/jsonify.dart
index f09ad7f95ee133c710346f90b10e6462ddf28949..54a6e1800d7deb094e475666b9922ce6e2c07ac0 100644
--- a/pkg/compiler/samples/jsonify/jsonify.dart
+++ b/pkg/compiler/samples/jsonify/jsonify.dart
@@ -70,7 +70,7 @@ jsonify(MirrorSystem mirrors) {
     BackDoor.compilationUnitsOf(library).forEach((compilationUnit) {
       Uri uri = compilationUnit.uri;
       String filename = relativize(sdkRoot, uri, false);
-      SourceFile file = handler.provider.sourceFiles['$uri'];
+      SourceFile file = handler.provider.sourceFiles[uri];
       map['sdk:/$filename'] = file.slowText();
     });
   });
@@ -80,7 +80,7 @@ jsonify(MirrorSystem mirrors) {
     if (patch != null) {
       Uri uri = sdkRoot.resolve('sdk/lib/$patch');
       String filename = relativize(sdkRoot, uri, false);
-      SourceFile file = handler.provider.sourceFiles['$uri'];
+      SourceFile file = handler.provider.sourceFiles[uri];
       map['sdk:/$filename'] = file.slowText();
     }
   });