Introduce initial plumbing for type inference in fasta.

pkg/front_end/test/subpackage_relationships_test.dart

Index: pkg/front_end/test/subpackage_relationships_test.dart
diff --git a/pkg/front_end/test/subpackage_relationships_test.dart b/pkg/front_end/test/subpackage_relationships_test.dart
index bd67d7869c18540cbe923dde1494df321fd6149b..6ac5adbf986c7c1419aa6cafd6a5e8463eba2106 100644
--- a/pkg/front_end/test/subpackage_relationships_test.dart
+++ b/pkg/front_end/test/subpackage_relationships_test.dart
@@ -68,6 +68,7 @@ final subpackageRules = {
     'lib/src/fasta/parser',
     'lib/src/fasta/scanner',
     'lib/src/fasta/source',
+    'lib/src/fasta/type_inference',
     'lib/src/fasta/util',
   ]),
   'lib/src/fasta/parser': new SubpackageRules(allowedDependencies: [
@@ -89,6 +90,7 @@ final subpackageRules = {
     'lib/src/fasta/kernel',
     'lib/src/fasta/parser',
     'lib/src/fasta/scanner',
+    'lib/src/fasta/type_inference',
     'lib/src/fasta/util',
   ]),
   'lib/src/fasta/testing':
@@ -99,6 +101,7 @@ final subpackageRules = {
     'lib/src/fasta/analyzer',
     'lib/src/fasta/scanner',
   ]),
+  'lib/src/fasta/type_inference': new SubpackageRules(),
   'lib/src/fasta/util': new SubpackageRules(),
   'lib/src/scanner': new SubpackageRules(allowedDependencies: [
     'lib/src/base',