Force another diagnostic reporting path to be warn-only on Windows.

tools/clang/plugins/ChromeClassTester.cpp

 // 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.
 
 // A general interface for filtering and only acting on classes in Chromium C++
 // code.
 
 #include "ChromeClassTester.h"
 
 #include <algorithm>
@@ skipping 77 matching lines @@
     CheckChromeEnum(enum_location, enum_decl);
   }
 }
 
 void ChromeClassTester::emitWarning(SourceLocation loc,
                                     const char* raw_error) {
   FullSourceLoc full(loc, instance().getSourceManager());
   std::string err;
   err = "[chromium-style] ";
   err += raw_error;
+  // TODO(dcheng): Re-enable -Werror for these diagnostics on Windows once all
+  // the pre-existing warnings are cleaned up. https://crbug.com/467287
   DiagnosticIDs::Level level =
+#if !defined(LLVM_ON_WIN32)
       diagnostic().getWarningsAsErrors() ?
       DiagnosticIDs::Error :
+#endif
       DiagnosticIDs::Warning;
   unsigned id = diagnostic().getDiagnosticIDs()->getCustomDiagID(level, err);
   DiagnosticBuilder builder = diagnostic().Report(full, id);
 }
 
 bool ChromeClassTester::InBannedNamespace(const Decl* record) {
   std::string n = GetNamespace(record);
   if (!n.empty()) {
     return std::find(banned_namespaces_.begin(), banned_namespaces_.end(), n)
         != banned_namespaces_.end();
@@ skipping 182 matching lines @@
   PresumedLoc ploc = source_manager.getPresumedLoc(spelling_location);
   if (ploc.isInvalid()) {
     // If we're in an invalid location, we're looking at things that aren't
     // actually stated in the source.
     return false;
   }
 
   *filename = ploc.getFilename();
   return true;
 }