renaming File to Source

test/common.dart

Index: test/common.dart
diff --git a/test/common.dart b/test/common.dart
index 708b96ec09a99e63e268d222f3992fdb46aadb61..661979b8573287025ce30f1347f6f1c3f2bdc936 100644
--- a/test/common.dart
+++ b/test/common.dart
@@ -18,7 +18,7 @@ int longName(int longVar2) {
   return longVar1 + longVar2;
 }
 ''';
-var input = new File.text('input.dart', INPUT);
+var input = new SourceFile.text('input.dart', INPUT);
 
 /// A span in the input file
 Span ispan(int start, int end, [bool isIdentifier = false]) =>
@@ -34,7 +34,7 @@ const String OUTPUT = '''
 var x = 3;
 f(y) => x + y;
 ''';
-var output = new File.text('output.dart', OUTPUT);
+var output = new SourceFile.text('output.dart', OUTPUT);
 
 /// A span in the output file
 Span ospan(int start, int end, [bool isIdentifier = false]) =>