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

ios/chrome/browser/net/retryable_url_fetcher_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.
 
 #import "ios/chrome/browser/net/retryable_url_fetcher.h"
 
 #import "base/mac/scoped_nsobject.h"
 #include "ios/web/public/test/test_web_thread.h"
 #include "net/url_request/test_url_fetcher_factory.h"
 #include "net/url_request/url_fetcher_delegate.h"
@@ skipping 35 matching lines @@
 class RetryableURLFetcherTest : public PlatformTest {
  protected:
   void SetUp() override {
     PlatformTest::SetUp();
     test_delegate_.reset([[TestRetryableURLFetcherDelegate alloc] init]);
     io_thread_.reset(
         new web::TestWebThread(web::WebThread::IO, &message_loop_));
   }
 
   net::TestURLFetcherFactory factory_;
-  scoped_ptr<web::TestWebThread> io_thread_;
+  std::unique_ptr<web::TestWebThread> io_thread_;
   base::MessageLoop message_loop_;
   base::scoped_nsobject<TestRetryableURLFetcherDelegate> test_delegate_;
 };
 
 TEST_F(RetryableURLFetcherTest, TestResponse200) {
   scoped_refptr<net::URLRequestContextGetter> request_context_getter =
       new net::TestURLRequestContextGetter(message_loop_.task_runner());
   base::scoped_nsobject<RetryableURLFetcher> retryableFetcher(
       [[RetryableURLFetcher alloc]
           initWithRequestContextGetter:request_context_getter.get()
@@ skipping 27 matching lines @@
   DCHECK(fetcher);
   DCHECK(fetcher->delegate());
   [test_delegate_ setResponsesProcessed:0U];
   fetcher->set_response_code(404);
   fetcher->SetResponseString("");
   fetcher->delegate()->OnURLFetchComplete(fetcher);
   EXPECT_EQ(0U, [test_delegate_ responsesProcessed]);
 }
 
 }  // namespace