[CRD iOS] Branching internal and external implementations

remoting/ios/app/remoting_resource_factory.mm

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
+#import "remoting/ios/app/remoting_resource_factory.h"
+
+#include "base/logging.h"
+
+static RemotingResourceFactory* defaultResourceFactory = nil;
+
+@implementation RemotingResourceFactory
+
+- (UIViewController*)wrapRootViewController:(UIViewController*)controller {
+  [NSException
+       raise:NSInternalInconsistencyException
+      format:@"Subclass must override the wrapRootViewController: method"];
+  return nil;
+}
+
+- (void)presentMenuOnController:(UIViewController*)controller {
+  [NSException
+       raise:NSInternalInconsistencyException
+      format:@"Subclass must override the presentMenuOnController: method"];
+}
+
+#pragma mark - Class Property
+
++ (RemotingResourceFactory*)defaultFactory {
+  DCHECK(defaultResourceFactory != nil) << "defaultFactory has never been set.";
+  return defaultResourceFactory;
+}
+
++ (void)setDefaultFactory:(RemotingResourceFactory*)factory {
+  defaultResourceFactory = factory;
+}
+
+@end