Do not qualify with dart:: except where necessary

runtime/vm/bootstrap.cc

Index: runtime/vm/bootstrap.cc
diff --git a/runtime/vm/bootstrap.cc b/runtime/vm/bootstrap.cc
index 48a41656e4f6a950da73b0a4428f272981e00784..c6e8d633007e315dc030431fbbca2e4528c2a054 100644
--- a/runtime/vm/bootstrap.cc
+++ b/runtime/vm/bootstrap.cc
@@ -310,7 +310,7 @@ static RawError* BootstrapFromKernel(Thread* thread, kernel::Program* program) {
   // adding classes to the list more than once.
   GrowableObjectArray& pending_classes = GrowableObjectArray::Handle(
       zone, isolate->object_store()->pending_classes());
-  dart::Class& pending = dart::Class::Handle(zone);
+  Class& pending = Class::Handle(zone);
   for (intptr_t i = 0; i < pending_classes.Length(); ++i) {
     pending ^= pending_classes.At(i);
     pending.set_is_marked_for_parsing();