Convert //ios from scoped_ptr to std::unique_ptr.

ios/web/navigation/navigation_manager_impl_unittest.mm

 // Copyright 2014 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.
 
 #include "base/logging.h"
 #include "ios/web/navigation/navigation_manager_impl.h"
 #include "ios/web/public/test/test_browser_state.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "testing/gtest_mac.h"
 #include "testing/platform_test.h"
 
 namespace web {
 namespace {
 
 class NavigationManagerTest : public PlatformTest {
  protected:
   void SetUp() override {
     manager_.reset(new NavigationManagerImpl(NULL, &browser_state_));
   }
-  scoped_ptr<NavigationManagerImpl> manager_;
+  std::unique_ptr<NavigationManagerImpl> manager_;
   TestBrowserState browser_state_;
 };
 
 // TODO(stuartmorgan): Remove this once NavigationManager has actual
 // functionality to test, instead of just being pass-throughs.
 TEST_F(NavigationManagerTest, Dummy) {
   EXPECT_FALSE(manager_->CanGoBack());
   EXPECT_FALSE(manager_->CanGoForward());
 }
 
 }  // namespace
 }  // namespace web