Implement incremental tests with multiple files.

dart/tests/try/poi/compiler_test_case.dart

Index: dart/tests/try/poi/compiler_test_case.dart
diff --git a/dart/tests/try/poi/compiler_test_case.dart b/dart/tests/try/poi/compiler_test_case.dart
index 7642364706385127b366501f6ffdf5c28c517f5d..8827c97a1cde6832e56f346da4ba3bf7aa377beb 100644
--- a/dart/tests/try/poi/compiler_test_case.dart
+++ b/dart/tests/try/poi/compiler_test_case.dart
@@ -31,7 +31,7 @@ const String CONSTANT_CLASS = 'class Constant { const Constant(); }';
 
 const String SCHEME = 'org.trydart.compiler-test-case';
 
-Uri customUri(String path) => Uri.parse('$SCHEME://$path');
+Uri customUri(String path) => Uri.parse('$SCHEME:/$path');
 
 Future runTests(List<CompilerTestCase> tests) {
   asyncTest(() => Future.forEach(tests, runTest));