Fix some case-insensitive cases for StartsWith

chrome/installer/util/install_util.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.
 //
 // See the corresponding header file for description of the functions in this
 // file.
 
 #include "chrome/installer/util/install_util.h"
 
 #include <shellapi.h>
@@ skipping 375 matching lines @@
 #else
         base::DIR_PROGRAM_FILES;
 #endif
     if (!PathService::Get(kProgramFilesKey, &program_files_path)) {
       NOTREACHED();
       return true;
     }
     env->SetVar(kEnvProgramFilesPath,
                 base::WideToUTF8(program_files_path.value()));
   }
-  return !base::StartsWith(exe_path.value(), program_files_path.value(), false);
+
+  // Return true if the program files path is not a case-insensitive prefix of
+  // the exe path.
+  if (exe_path.value().size() < program_files_path.value().size())
+    return true;
+  DWORD prefix_len = static_cast<DWORD>(program_files_path.value().size());

[grt (UTC plus 2), 2015/07/01 17:55:42]

base::saturated_cast<DWORD, size_t>()?

+  return ::CompareString(LOCALE_USER_DEFAULT, NORM_IGNORECASE,
+                         exe_path.value().data(), prefix_len,
+                         program_files_path.value().data(), prefix_len) !=
+      CSTR_EQUAL;
 }
 
 bool InstallUtil::IsMultiInstall(BrowserDistribution* dist,
                                  bool system_install) {
   DCHECK(dist);
   ProductState state;
   return state.Initialize(system_install, dist) && state.is_multi_install();
 }
 
 bool CheckIsChromeSxSProcess() {
@@ skipping 258 matching lines @@
   // Open the program and see if it references the expected file.
   base::File file;
   BY_HANDLE_FILE_INFORMATION info = {};
 
   return (OpenForInfo(path, &file) &&
           GetInfo(file, &info) &&
           info.dwVolumeSerialNumber == file_info_.dwVolumeSerialNumber &&
           info.nFileIndexHigh == file_info_.nFileIndexHigh &&
           info.nFileIndexLow == file_info_.nFileIndexLow);
 }