Use common.dart to re-export commonly used entities.

pkg/compiler/lib/src/inferrer/simple_types_inferrer.dart

Index: pkg/compiler/lib/src/inferrer/simple_types_inferrer.dart
diff --git a/pkg/compiler/lib/src/inferrer/simple_types_inferrer.dart b/pkg/compiler/lib/src/inferrer/simple_types_inferrer.dart
index 30c9c8c4a651b5c37eca67ed7b3734fee90a2328..150dca10de58d48dc1f07d1f5fd90383cfc6c3c9 100644
--- a/pkg/compiler/lib/src/inferrer/simple_types_inferrer.dart
+++ b/pkg/compiler/lib/src/inferrer/simple_types_inferrer.dart
@@ -7,6 +7,7 @@ library simple_types_inferrer;
 import '../closure.dart' show
     ClosureClassMap,
     ClosureScope;
+import '../common.dart';
 import '../common/names.dart' show
     Selectors;
 import '../compiler.dart' show
@@ -21,8 +22,6 @@ import '../dart_types.dart' show
     FunctionType,
     InterfaceType,
     TypeKind;
-import '../diagnostics/spannable.dart' show
-    Spannable;
 import '../elements/elements.dart';
 import '../js_backend/js_backend.dart' as js;
 import '../native/native.dart' as native;