Support more configurability in GN toolchains

tools/gn/source_file_type.cc

Index: tools/gn/source_file_type.cc
diff --git a/tools/gn/source_file_type.cc b/tools/gn/source_file_type.cc
new file mode 100644
index 0000000000000000000000000000000000000000..b58ecb372f326961a037da774d0d02329ae8a447
--- /dev/null
+++ b/tools/gn/source_file_type.cc
@@ -0,0 +1,31 @@
+// Copyright 2014 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/source_file_type.h"
+
+#include "tools/gn/filesystem_utils.h"
+#include "tools/gn/source_file.h"
+
+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;
+  if (extension == "m")
+    return SOURCE_M;
+  if (extension == "mm")
+    return SOURCE_MM;
+  if (extension == "rc")
+    return SOURCE_RC;
+  if (extension == "S" || extension == "s")
+    return SOURCE_S;
+  if (extension == "o" || extension == "obj")
+    return SOURCE_O;
+
+  return SOURCE_UNKNOWN;
+}
+