Remove legacy StartsWithASCII function.

tools/gn/header_checker.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 "tools/gn/header_checker.h"
 
 #include <algorithm>
 
 #include "base/bind.h"
 #include "base/files/file_util.h"
@@ skipping 19 matching lines @@
   bool is_generated;
 };
 
 // If the given file is in the "gen" folder, trims this so it treats the gen
 // directory as the source root:
 //   //out/Debug/gen/foo/bar.h -> //foo/bar.h
 // If the file isn't in the generated root, returns the input unchanged.
 SourceFile RemoveRootGenDirFromFile(const Target* target,
                                     const SourceFile& file) {
   const SourceDir& gen = target->settings()->toolchain_gen_dir();
-  if (!gen.is_null() && base::StartsWithASCII(file.value(), gen.value(), true))
+  if (!gen.is_null() && base::StartsWith(file.value(), gen.value(),
+                                         base::CompareCase::SENSITIVE))
     return SourceFile("//" + file.value().substr(gen.value().size()));
   return file;
 }
 
 // This class makes InputFiles on the stack as it reads files to check. When
 // we throw an error, the Err indicates a locatin which has a pointer to
 // an InputFile that must persist as long as the Err does.
 //
 // To make this work, this function creates a clone of the InputFile managed
 // by the InputFileManager so the error can refer to something that
@@ skipping 523 matching lines @@
   if (targets_with_other_toolchains.size() +
       targets_with_matching_toolchains.size() > 1)
     msg += "at least one of ";
   msg += "which should somehow be reachable.";
 
   // Danger: must call CreatePersistentRange to put in Err.
   return Err(CreatePersistentRange(source_file, range),
              "Include not allowed.", msg);
 }