Fix for mapping SDK files to 'dart:' URIs.

pkg/analysis_server/lib/src/domain_execution.dart

Index: pkg/analysis_server/lib/src/domain_execution.dart
diff --git a/pkg/analysis_server/lib/src/domain_execution.dart b/pkg/analysis_server/lib/src/domain_execution.dart
index 470d3c330dacec6ad354b89e5b4de8c8609b1423..c2f8a5a09ebe32f89dd168c83136b9791499c172 100644
--- a/pkg/analysis_server/lib/src/domain_execution.dart
+++ b/pkg/analysis_server/lib/src/domain_execution.dart
@@ -117,7 +117,11 @@ class ExecutionDomainHandler implements RequestHandler {
       }
       ContextSourcePair contextSource = server.getContextSourcePair(file);
       Source source = contextSource.source;
-      uri = context.sourceFactory.restoreUri(source).toString();
+      if (source.uriKind != UriKind.FILE_URI) {
+        uri = source.uri.toString();
+      } else {
+        uri = context.sourceFactory.restoreUri(source).toString();
+      }
       return new ExecutionMapUriResult(uri: uri).toResponse(request.id);
     } else if (uri != null) {
       Source source = context.sourceFactory.forUri(uri);