Use URIs rather than paths in front end API.

pkg/front_end/tool/example.dart

Index: pkg/front_end/tool/example.dart
diff --git a/pkg/front_end/tool/example.dart b/pkg/front_end/tool/example.dart
index 1d49b228759959446c8f8ffb560b6f9a4747ed5a..d81f43746e36388e4f684f8e12e055bff0a584cb 100644
--- a/pkg/front_end/tool/example.dart
+++ b/pkg/front_end/tool/example.dart
@@ -11,17 +11,19 @@ Future dumpToSink(Program program, StreamSink<List<int>> sink) {
 }
 
 Future kernelToSink(Uri entry, StreamSink<List<int>> sink) async {
-  var program = await kernelForProgram(entry,
+  var program = await kernelForProgram(
+      entry,
       new CompilerOptions()
-        ..sdkPath = 'sdk'
-        ..packagesFilePath = '.packages'
+        ..sdkRoot = new Uri.file('sdk')
+        ..packagesFileUri = new Uri.file('.packages')
         ..onError = (e) => print(e.message));
 
   await dumpToSink(program, sink);
 }
 
 main(args) async {
-  kernelToSink(Uri.base.resolve(args[0]),
+  kernelToSink(
+      Uri.base.resolve(args[0]),
       // TODO(sigmund,hausner): define memory type where to dump binary data.
       new StreamController<List<int>>.broadcast().sink);
 }