Set 'isSyntheticDefault' for default constructors.

pkg/front_end/testcases/inference/infer_assign_to_property_super_upwards.dart.strong.expect

 library test;
 import self as self;
 import "dart:core" as core;
 
 class Base extends core::Object {
   field core::int intProp = null;
   field core::num numProp = null;
   field core::double doubleProp = null;
-  constructor •() → void
+  default constructor •() → void
     : super core::Object::•()
     ;
 }
 class Test1 extends self::Base {
-  constructor •() → void
+  default constructor •() → void
     : super self::Base::•()
     ;
   method test() → void {
     core::int v1 = super.{self::Base::intProp} = self::getInt();
     core::num v2 = super.{self::Base::intProp} = self::getNum();
     core::int v4 = let final dynamic #t1 = super.{self::Base::intProp} in #t1.{core::num::==}(null) ? super.{self::Base::intProp} = self::getInt() : #t1;
     core::num v5 = let final dynamic #t2 = super.{self::Base::intProp} in #t2.{core::num::==}(null) ? super.{self::Base::intProp} = self::getNum() : #t2;
     core::int v7 = super.{self::Base::intProp} = super.{self::Base::intProp}.{core::num::+}(self::getInt());
     core::num v8 = super.{self::Base::intProp} = super.{self::Base::intProp}.{core::num::+}(self::getNum());
     core::int v10 = super.{self::Base::intProp} = super.{self::Base::intProp}.{core::num::+}(1);
     core::int v11 = let final dynamic #t3 = super.{self::Base::intProp} in let final dynamic #t4 = super.{self::Base::intProp} = #t3.{core::num::+}(1) in #t3;
   }
 }
 class Test2 extends self::Base {
-  constructor •() → void
+  default constructor •() → void
     : super self::Base::•()
     ;
   method test() → void {
     core::int v1 = super.{self::Base::numProp} = self::getInt();
     core::num v2 = super.{self::Base::numProp} = self::getNum();
     core::double v3 = super.{self::Base::numProp} = self::getDouble();
     core::num v4 = let final dynamic #t5 = super.{self::Base::numProp} in #t5.{core::num::==}(null) ? super.{self::Base::numProp} = self::getInt() : #t5;
     core::num v5 = let final dynamic #t6 = super.{self::Base::numProp} in #t6.{core::num::==}(null) ? super.{self::Base::numProp} = self::getNum() : #t6;
     core::num v6 = let final dynamic #t7 = super.{self::Base::numProp} in #t7.{core::num::==}(null) ? super.{self::Base::numProp} = self::getDouble() : #t7;
     core::num v7 = super.{self::Base::numProp} = super.{self::Base::numProp}.{core::num::+}(self::getInt());
     core::num v8 = super.{self::Base::numProp} = super.{self::Base::numProp}.{core::num::+}(self::getNum());
     core::num v9 = super.{self::Base::numProp} = super.{self::Base::numProp}.{core::num::+}(self::getDouble());
     core::num v10 = super.{self::Base::numProp} = super.{self::Base::numProp}.{core::num::+}(1);
     core::num v11 = let final dynamic #t8 = super.{self::Base::numProp} in let final dynamic #t9 = super.{self::Base::numProp} = #t8.{core::num::+}(1) in #t8;
   }
 }
 class Test3 extends self::Base {
-  constructor •() → void
+  default constructor •() → void
     : super self::Base::•()
     ;
   method test3() → void {
     core::num v2 = super.{self::Base::doubleProp} = self::getNum();
     core::double v3 = super.{self::Base::doubleProp} = self::getDouble();
     core::num v5 = let final dynamic #t10 = super.{self::Base::doubleProp} in #t10.{core::num::==}(null) ? super.{self::Base::doubleProp} = self::getNum() : #t10;
     core::double v6 = let final dynamic #t11 = super.{self::Base::doubleProp} in #t11.{core::num::==}(null) ? super.{self::Base::doubleProp} = self::getDouble() : #t11;
     core::double v7 = super.{self::Base::doubleProp} = super.{self::Base::doubleProp}.{core::double::+}(self::getInt());
     core::double v8 = super.{self::Base::doubleProp} = super.{self::Base::doubleProp}.{core::double::+}(self::getNum());
     core::double v9 = super.{self::Base::doubleProp} = super.{self::Base::doubleProp}.{core::double::+}(self::getDouble());
     core::double v10 = super.{self::Base::doubleProp} = super.{self::Base::doubleProp}.{core::double::+}(1);
     core::double v11 = let final dynamic #t12 = super.{self::Base::doubleProp} in let final dynamic #t13 = super.{self::Base::doubleProp} = #t12.{core::double::+}(1) in #t12;
   }
 }
 static method getInt() → core::int
   return 0;
 static method getNum() → core::num
   return 0;
 static method getDouble() → core::double
   return 0.0;
 static method main() → dynamic {}