Replace string::find(prefix) == 0 pattern with base::StartsWith().

chrome/browser/download/download_browsertest.cc

 // Copyright (c) 2012 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 "chrome/browser/download/download_browsertest.h"
 
 #include <stdint.h>
 #include <sstream>
 #include <utility>
 
@@ skipping 2540 matching lines @@
 //    C -> S: GET /foo
 //            Referer: http://example.com/foo
 //    S -> C: HTTP/1.1 200 OK
 //            Content-Type: text/plain
 //
 //            http://example.com/foo
 static std::unique_ptr<net::test_server::HttpResponse>
 EchoReferrerRequestHandler(const net::test_server::HttpRequest& request) {
   const std::string kReferrerHeader = "Referer";  // SIC
 
-  if (request.relative_url.find("/echoreferrer") != 0)
+  if (!base::StartsWith(request.relative_url, "/echoreferrer",
+                        base::CompareCase::SENSITIVE)) {
     return std::unique_ptr<net::test_server::HttpResponse>();
+  }
 
   std::unique_ptr<net::test_server::BasicHttpResponse> response(
       new net::test_server::BasicHttpResponse());
   response->set_code(net::HTTP_OK);
   response->set_content_type("text/plain");
   auto referrer_header = request.headers.find(kReferrerHeader);
   if (referrer_header != request.headers.end())
     response->set_content(referrer_header->second);
   return std::move(response);
 }
@@ skipping 1096 matching lines @@
       DangerousDownloadWaiter(
           browser(), 1,
           content::DownloadTestObserver::ON_DANGEROUS_DOWNLOAD_DENY));
   ui_test_utils::NavigateToURL(browser(), extension_url);
 
   observer->WaitForFinished();
 
   // Download shelf should close.
   EXPECT_FALSE(browser()->window()->IsDownloadShelfVisible());
 }