Use exact name lookup for static fields in mirrors.

runtime/lib/mirrors.cc

Index: runtime/lib/mirrors.cc
diff --git a/runtime/lib/mirrors.cc b/runtime/lib/mirrors.cc
index 7a1194b6826969e8ae8fbdec4d8a0f12c86125c2..40efc283c9d7cdfd56d2e07404124c037fcff2d8 100644
--- a/runtime/lib/mirrors.cc
+++ b/runtime/lib/mirrors.cc
@@ -718,7 +718,7 @@ static RawInstance* InvokeClassGetter(const Class& klass,
                                       const bool throw_nsm_if_absent) {
   // Note static fields do not have implicit getters.
   const Field& field =
-      Field::Handle(klass.LookupStaticFieldAllowPrivate(getter_name));
+      Field::Handle(klass.LookupStaticField(getter_name));
   if (field.IsNull() || field.IsUninitialized()) {
     const String& internal_getter_name = String::Handle(
         Field::GetterName(getter_name));
@@ -1571,7 +1571,7 @@ DEFINE_NATIVE_ENTRY(ClassMirror_invokeSetter, 4) {
 
   // Check for real fields and user-defined setters.
   const Field& field =
-      Field::Handle(klass.LookupStaticFieldAllowPrivate(setter_name));
+      Field::Handle(klass.LookupStaticField(setter_name));
   Function& setter = Function::Handle();
   const String& internal_setter_name = String::Handle(
       Field::SetterName(setter_name));