clang/win: Fix -Wsign-compare warning after https://codereview.chromium.org/1631903002

chrome/installer/test/alternate_version_generator.cc

 // Copyright (c) 2011 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.
 
 // The file contains the implementation of the mini_installer re-versioner.
 // The main function (GenerateNextVersion) does the following in a temp dir:
 // - Extracts and unpacks setup.exe and the Chrome-bin folder from
 //   mini_installer.exe.
 // - Inspects setup.exe to determine the current version.
 // - Runs through all .dll and .exe files:
@@ skipping 407 matching lines @@
   std::string new_version(context->new_version.ToASCII());
   bool modified = false;
   if (!ReplaceAll(reinterpret_cast<uint8_t*>(&contents[0]),
                   reinterpret_cast<uint8_t*>(&contents[contents.size()]),
                   reinterpret_cast<uint8_t*>(&old_version[0]),
                   reinterpret_cast<uint8_t*>(&old_version[old_version.size()]),
                   reinterpret_cast<uint8_t*>(&new_version[0]), &modified)) {
     return false;
   }
   DCHECK(modified);
-  return base::WriteFile(manifest, &contents[0], contents.size()) ==
-         contents.size();
+  int written = base::WriteFile(manifest, &contents[0], contents.size());
+  return written != -1 && static_cast<size_t>(written) == contents.size();
 }
 
 bool IncrementNewVersion(upgrade_test::Direction direction,
                          VisitResourceContext* ctx) {
   DCHECK(ctx);
 
   // Figure out a past or future version with the same string length as this one
   // by decrementing or incrementing each component.
   LONGLONG incrementer = (direction == upgrade_test::PREVIOUS_VERSION ? -1 : 1);
 
@@ skipping 322 matching lines @@
     return false;
   }
   ctx.current_version_str = ctx.current_version.ToString();
   ctx.new_version = ChromeVersion::FromString(version.GetString());
   ctx.new_version_str = ctx.new_version.ToString();
 
   return UpdateVersionIfMatch(target_file, &ctx);
 }
 
 }  // namespace upgrade_test