Compute mixin application constructors in the ClassElement.constructors getter.

pkg/analyzer/test/generated/all_the_rest_test.dart

Index: pkg/analyzer/test/generated/all_the_rest_test.dart
diff --git a/pkg/analyzer/test/generated/all_the_rest_test.dart b/pkg/analyzer/test/generated/all_the_rest_test.dart
index e163fd06e83d157622eaccb25bf6f6baccc80c4e..0a1b03a5778ccb30aea5b067d3142245d78d44d6 100644
--- a/pkg/analyzer/test/generated/all_the_rest_test.dart
+++ b/pkg/analyzer/test/generated/all_the_rest_test.dart
@@ -1061,6 +1061,8 @@ class ConstantFinderTest extends EngineTestCase {
           ElementFactory.constructorElement(classElement, '', true);
       constructorDeclaration.element = constructorElement;
       classElement.constructors = <ConstructorElement>[constructorElement];
+    } else {
+      classElement.constructors = ConstructorElement.EMPTY_LIST;
     }
     return variableDeclaration;
   }
@@ -8256,7 +8258,6 @@ final Map<String, LibraryInfo> LIBRARIES = const <String, LibraryInfo> {
   }
 }
 
-
 @reflectiveTest
 class StringScannerTest extends AbstractScannerTest {
   @override