Fix breaking change from next SDK

bin/dwc_browser.dart

Index: bin/dwc_browser.dart
diff --git a/bin/dwc_browser.dart b/bin/dwc_browser.dart
index 234c333679b279a45cf335e2f8315009b9981eaf..772ae44a99e96fb2aae48ed1d020be280100dac0 100644
--- a/bin/dwc_browser.dart
+++ b/bin/dwc_browser.dart
@@ -37,7 +37,7 @@ void parse(js.Proxy sourcePagePort, String sourceUri) {
   // TODO(jacobr): we need to send error messages back to sourcePagePort.
   js.retain(sourcePagePort);
   print("Processing: $sourceUri");
-  Uri uri = new Uri.fromString(sourceUri);
+  Uri uri = Uri.parse(sourceUri);
   fileSystem = new BrowserFileSystem(uri.scheme, sourcePagePort);
   // TODO(jacobr): provide a way to pass in options.
   var options = CompilerOptions.parse(['--no-colors', uri.path]);