Add a toUri method to Resource

pkg/analyzer/lib/file_system/memory_file_system.dart

Index: pkg/analyzer/lib/file_system/memory_file_system.dart
diff --git a/pkg/analyzer/lib/file_system/memory_file_system.dart b/pkg/analyzer/lib/file_system/memory_file_system.dart
index 1943ddf2ba4f21535b3d230dea190912c357ec2f..cd8e14909cd26fcaeafbe5d77585426a751f3195 100644
--- a/pkg/analyzer/lib/file_system/memory_file_system.dart
+++ b/pkg/analyzer/lib/file_system/memory_file_system.dart
@@ -314,6 +314,9 @@ class _MemoryDummyLink extends _MemoryResource implements File {
   }
 
   @override
+  Uri toUri() => new Uri.file(path, windows: _provider.pathContext == windows);
+
+  @override
   void writeAsBytesSync(List<int> bytes) {
     throw new FileSystemException(path, 'File could not be written');
   }
@@ -388,6 +391,9 @@ class _MemoryFile extends _MemoryResource implements File {
   }
 
   @override
+  Uri toUri() => new Uri.file(path, windows: _provider.pathContext == windows);
+
+  @override
   void writeAsBytesSync(List<int> bytes) {
     _provider._setFileBytes(this, bytes);
   }
@@ -561,6 +567,10 @@ class _MemoryFolder extends _MemoryResource implements Folder {
     }
     return contains(path);
   }
+
+  @override
+  Uri toUri() =>
+      new Uri.directory(path, windows: _provider.pathContext == windows);
 }
 
 /**