Fix and enable MSVC warning C4018 for base/.

base/files/file_enumerator_win.cc

 // Copyright (c) 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 "base/files/file_enumerator.h"
 
 #include <string.h>
 
 #include "base/logging.h"
 #include "base/threading/thread_restrictions.h"
@@ skipping 12 matching lines @@
 }
 
 FilePath FileEnumerator::FileInfo::GetName() const {
   return FilePath(find_data_.cFileName);
 }
 
 int64 FileEnumerator::FileInfo::GetSize() const {
   ULARGE_INTEGER size;
   size.HighPart = find_data_.nFileSizeHigh;
   size.LowPart = find_data_.nFileSizeLow;
-  DCHECK_LE(size.QuadPart, std::numeric_limits<int64>::max());
+  DCHECK_LE(size.QuadPart,
+            static_cast<ULONGLONG>(std::numeric_limits<int64>::max()));

[Nico, 2015/07/20 23:39:27]

Does std::numeric_limits<ULONGLONG>::max() not work?

[Peter Kasting, 2015/07/20 23:45:50]

That's not correct.  We're going to cast a ULONGLONG to an int64, so we want to
check that it's not over the int64 max.  Checking against ULONGLONG max would
tautologically be true.

[Nico, 2015/07/20 23:48:09]

Ah, I see.

   return static_cast<int64>(size.QuadPart);
 }
 
 base::Time FileEnumerator::FileInfo::GetLastModifiedTime() const {
   return base::Time::FromFileTime(find_data_.ftLastWriteTime);
 }
 
 // FileEnumerator --------------------------------------------------------------
 
 FileEnumerator::FileEnumerator(const FilePath& root_path,
@@ skipping 111 matching lines @@
         return cur_file;
     } else if (file_type_ & FileEnumerator::FILES) {
       return cur_file;
     }
   }
 
   return FilePath();
 }
 
 }  // namespace base