Add optional public header checking to GN build

tools/gn/filesystem_utils.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 "tools/gn/filesystem_utils.h"
 
 #include <algorithm>
 
 #include "base/file_util.h"
 #include "base/logging.h"
@@ skipping 147 matching lines @@
   return ::CompareString(LOCALE_USER_DEFAULT, LINGUISTIC_IGNORECASE,
                          a.c_str(), -1, b.c_str(), -1) == CSTR_EQUAL;
 #else
   // Assume case-sensitive filesystems on non-Windows.
   return a == b;
 #endif
 }
 
 }  // namespace
 
-SourceFileType GetSourceFileType(const SourceFile& file,
-                                 Settings::TargetOS os) {
+SourceFileType GetSourceFileType(const SourceFile& file) {
   base::StringPiece extension = FindExtension(&file.value());
   if (extension == "cc" || extension == "cpp" || extension == "cxx")
     return SOURCE_CC;
   if (extension == "h")
     return SOURCE_H;
   if (extension == "c")
     return SOURCE_C;
-
-  switch (os) {
-    case Settings::MAC:
-      if (extension == "m")
-        return SOURCE_M;
-      if (extension == "mm")
-        return SOURCE_MM;
-      break;
-
-    case Settings::WIN:
-      if (extension == "rc")
-        return SOURCE_RC;
-      // TODO(brettw) asm files.
-      break;
-
-    default:
-      break;
-  }
-
-  if (os != Settings::WIN) {
-    if (extension == "S")
-      return SOURCE_S;
-  }
+  if (extension == "m")
+    return SOURCE_M;
+  if (extension == "mm")
+    return SOURCE_MM;
+  if (extension == "rc")
+    return SOURCE_RC;
+  if (extension == "S")
+    return SOURCE_S;
 
   return SOURCE_UNKNOWN;
 }
 
 const char* GetExtensionForOutputType(Target::OutputType type,
                                       Settings::TargetOS os) {
   switch (os) {
     case Settings::MAC:
       switch (type) {
         case Target::EXECUTABLE:
@@ skipping 514 matching lines @@
   return GetGenDirForSourceDir(target->settings(), target->label().dir());
 }
 
 SourceDir GetCurrentOutputDir(const Scope* scope) {
   return GetOutputDirForSourceDir(scope->settings(), scope->GetSourceDir());
 }
 
 SourceDir GetCurrentGenDir(const Scope* scope) {
   return GetGenDirForSourceDir(scope->settings(), scope->GetSourceDir());
 }