Run dartfmt on kernel package

pkg/kernel/testcases/input/escape.dart

 class A {
   var field;
 }
+
 class B {
   var field;
 }
+
 class C {
-  operator==(x) => false;
+  operator ==(x) => false;
 }
 
 class X implements A, B {
   var field;
 }
 
 void useAsA(A object) {
   var _ = object.field;
 }
 
@@ skipping 14 matching lines @@
   // escape("");
   // escape(45);
 
   var object = new X();
   useAsA(new A());
   useAsA(object);
 
   useAsB(new B());
   useAsB(object);
 }