Add model test of CodegenWorldBuilder to compile_from_dill_test

pkg/compiler/lib/src/universe/member_usage.dart

Index: pkg/compiler/lib/src/universe/member_usage.dart
diff --git a/pkg/compiler/lib/src/universe/member_usage.dart b/pkg/compiler/lib/src/universe/member_usage.dart
index 08b37c96f5e2f2e76ffc2d5eb4a6ec66521dff7d..b58e5a28a14737a6dd1f0088a60695f3d5aaf0ab 100644
--- a/pkg/compiler/lib/src/universe/member_usage.dart
+++ b/pkg/compiler/lib/src/universe/member_usage.dart
@@ -21,6 +21,15 @@ abstract class _AbstractUsage<T> {
 
   /// `true` if the [appliedUse] is non-empty.
   bool get hasUse => appliedUse.isNotEmpty;
+
+  int get hashCode => _originalUse.hashCode * 13 + _pendingUse.hashCode * 17;
+
+  bool operator ==(other) {
+    if (identical(this, other)) return true;
+    if (other is! _AbstractUsage) return false;
+    return _originalUse.value == other._originalUse.value &&
+        _pendingUse.value == other._pendingUse.value;
+  }
 }
 
 /// Registry for the observed use of a member [entity] in the open world.