Remove legacy StartsWithASCII function.

ios/chrome/app/safe_mode_util_unittest.cc

 // Copyright 2013 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 <string.h>
 
 #include "base/files/file_path.h"
 #include "base/strings/string_util.h"
 #include "ios/chrome/app/safe_mode_util.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "testing/platform_test.h"
 
 using std::string;
 using std::vector;
 
 namespace {
 
 typedef PlatformTest SafeModeUtilTest;
 
 TEST_F(SafeModeUtilTest, GetAllImages) {
   vector<string> images = safe_mode_util::GetLoadedImages(nullptr);
   // There should be loaded images.
   EXPECT_GT(images.size(), 0U);
 
   // The libSystem dylib should always be present.
   bool found_lib_system = false;
   string lib_system_prefix("libSystem");
   for (size_t i = 0; i < images.size(); ++i) {
     string base_name = base::FilePath(images[i]).BaseName().value();
-    if (base::StartsWithASCII(base_name, lib_system_prefix, true)) {
+    if (base::StartsWith(base_name, lib_system_prefix,
+                         base::CompareCase::SENSITIVE)) {
       found_lib_system = true;
       break;
     }
   }
   EXPECT_TRUE(found_lib_system);
 }
 
 TEST_F(SafeModeUtilTest, GetSomeImages) {
   vector<string> all_images = safe_mode_util::GetLoadedImages(nullptr);
   vector<string> usr_lib_images = safe_mode_util::GetLoadedImages("/usr/lib/");
   // There should be images under /usr/lib/, but not all of them are.
   EXPECT_GT(usr_lib_images.size(), 0U);
   EXPECT_LT(usr_lib_images.size(), all_images.size());
 }
 
 }  // namespace