Set 'isSyntheticDefault' for default constructors.

pkg/front_end/testcases/inference/infer_field_override_multiple.dart.outline.expect

Index: pkg/front_end/testcases/inference/infer_field_override_multiple.dart.outline.expect
diff --git a/pkg/front_end/testcases/inference/infer_field_override_multiple.dart.outline.expect b/pkg/front_end/testcases/inference/infer_field_override_multiple.dart.outline.expect
index 39afce304b598813e66666de246fd4321d78544b..6328df632e3c27380cb1897fe8e387403a78b978 100644
--- a/pkg/front_end/testcases/inference/infer_field_override_multiple.dart.outline.expect
+++ b/pkg/front_end/testcases/inference/infer_field_override_multiple.dart.outline.expect
@@ -3,43 +3,43 @@ import self as self;
 import "dart:core" as core;
 
 abstract class A extends core::Object {
-  constructor •() → void
+  default constructor •() → void
     ;
   abstract get x() → core::int;
 }
 abstract class B extends core::Object {
-  constructor •() → void
+  default constructor •() → void
     ;
   abstract get x() → core::int;
 }
 abstract class C extends core::Object {
-  constructor •() → void
+  default constructor •() → void
     ;
   abstract get x() → core::num;
 }
 abstract class D extends core::Object {
-  constructor •() → void
+  default constructor •() → void
     ;
   abstract get x() → core::double;
 }
 class E extends self::A implements self::B {
   field dynamic x;
-  constructor •() → void
+  default constructor •() → void
     ;
 }
 class F extends self::A implements self::C {
   field dynamic x;
-  constructor •() → void
+  default constructor •() → void
     ;
 }
 class G extends self::A implements self::D {
   field dynamic x;
-  constructor •() → void
+  default constructor •() → void
     ;
 }
 class H extends self::C implements self::D {
   field dynamic x;
-  constructor •() → void
+  default constructor •() → void
     ;
 }
 static method main() → dynamic