Remove legacy StartsWithASCII function.

extensions/shell/common/shell_content_client_unittest.cc

 // 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 "extensions/shell/common/shell_content_client.h"
 
 #include <string>
 
 #include "base/strings/pattern.h"
 #include "base/strings/string_util.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 typedef testing::Test ShellContentClientTest;
 
 namespace extensions {
 
 // Tests that the app_shell user agent looks like a Chrome user agent.
 TEST_F(ShellContentClientTest, UserAgentFormat) {
   ShellContentClient client;
   std::string user_agent = client.GetUserAgent();
 
   // Must start with the usual Mozilla-compatibility string.
-  EXPECT_TRUE(base::StartsWithASCII(user_agent, "Mozilla/5.0", false))
+  EXPECT_TRUE(base::StartsWith(user_agent, "Mozilla/5.0",
+                               base::CompareCase::INSENSITIVE_ASCII))
       << user_agent;
 
   // Must contain a substring like "Chrome/1.2.3.4".
   EXPECT_TRUE(base::MatchPattern(user_agent, "*Chrome/*.*.*.*")) << user_agent;
 }
 
 }  // namespace extensions