Implement net in GN build.

tools/gn/ninja_helper.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/ninja_helper.h"
 
 #include "base/logging.h"
 #include "tools/gn/filesystem_utils.h"
 #include "tools/gn/string_utils.h"
 #include "tools/gn/target.h"
@@ skipping 194 matching lines @@
                                               SourceFileType type) const {
   // This function may be hot since it will be called for every source file
   // in the tree. We could cache the results to avoid making a string for
   // every invocation.
   std::string prefix = GetRulePrefix(settings);
 
   if (type == SOURCE_C)
     return prefix + "cc";
   if (type == SOURCE_CC)
     return prefix + "cxx";
+  if (type == SOURCE_M)
+    return prefix + "objc";
+  if (type == SOURCE_MM)
+    return prefix + "objcxx";
+  if (type == SOURCE_RC)
+    return prefix + "rc";
+  if (type == SOURCE_S)
+    return prefix + "cc";  // Assembly files just get compiled by CC.
 
   // TODO(brettw) asm files.
 
-  if (settings->IsMac()) {
-    if (type == SOURCE_M)
-      return prefix + "objc";
-    if (type == SOURCE_MM)
-      return prefix + "objcxx";
-  }
-
-  if (settings->IsWin()) {
-    if (type == SOURCE_RC)
-      return prefix + "rc";
-  } else {
-    if (type == SOURCE_S)
-      return prefix + "cc";  // Assembly files just get compiled by CC.
-  }
-
   return std::string();
 }