Remove bad URI (issue 25596)

R=pquitslund@google.com

Review URL: https://codereview.chromium.org/1806843003 .
diff --git a/pkg/analyzer/lib/analyzer.dart b/pkg/analyzer/lib/analyzer.dart
index 5cbc96a..0454992 100644
--- a/pkg/analyzer/lib/analyzer.dart
+++ b/pkg/analyzer/lib/analyzer.dart
@@ -77,7 +77,6 @@
 /// [suppressErrors] is `true`, in which case any errors are discarded.
 CompilationUnit parseDirectives(String contents,
     {String name, bool suppressErrors: false}) {
-  if (name == null) name = '<unknown source>';
   var source = new StringSource(contents, name);
   var errorCollector = new _ErrorCollector();
   var reader = new CharSequenceReader(contents);