Add "service_2" to CFE's list of opted out directories.

Change-Id: Ic63216b195e620e6f5d1955e37370b49efc30f17
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/167920
Auto-Submit: Bob Nystrom <[email protected]>
Commit-Queue: Johnni Winther <[email protected]>
Reviewed-by: Johnni Winther <[email protected]>

Author: munificent

pkg/front_end/lib/src/fasta/source/source_library_builder.dart

@@ -479,6 +479,7 @@ class SourceLibraryBuilder extends LibraryBuilderImpl {
     'ffi_2',
     'language_2/',
     'lib_2/',
+    'service_2/',
     'standalone_2/',
     'vm/dart_2/', // in runtime/tests
   ];