Fix deferred bug: when type argument is never instantiated

pkg/compiler/lib/src/deferred_load.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library deferred_load;
 
 import 'common/tasks.dart' show CompilerTask;
 import 'common.dart';
 import 'compiler.dart' show Compiler;
 import 'constants/expressions.dart' show ConstantExpression;
@@ skipping 301 matching lines @@
           collectTypeDependencies(argumentType);
         }
         for (ResolutionDartType argumentType in type.namedParameterTypes) {
           collectTypeDependencies(argumentType);
         }
         collectTypeDependencies(type.returnType);
       } else if (type is ResolutionTypedefType) {
         elements.add(type.element);
         collectTypeDependencies(type.unaliased);
       } else if (type is ResolutionInterfaceType) {
-        elements.add(type.element);
+        if (elements.add(type.element)) {
+          collectTypeDependencies(type.element.supertype);

[Siggi Cherem (dart-lang), 2017/08/11 21:34:52]

I believe this may be including transitive deps, which is not the coal for the
_collectAllElementsAndConstantsResolvedFrom(...)

I propose this alternative fix instead:
https://codereview.chromium.org/3000843002/

+        }
       }
     }
 
     /// Collects all direct dependencies of [element].
     ///
     /// The collected dependent elements and constants are are added to
     /// [elements] and [constants] respectively.
     void collectDependencies(Element element) {
       // TODO(johnniwinther): Remove this when [AbstractFieldElement] has been
       // removed.
@@ skipping 789 matching lines @@
 
   bool operator ==(other) {
     if (other is! _DeclaredDeferredImport) return false;
     return declaration == other.declaration;
   }
 
   int get hashCode => declaration.hashCode * 17;
 
   String toString() => '$declaration';
 }