Pass scroll bar placement as an enum instead of std::string

public/platform/mac/MacScrollTypes.h

Index: public/platform/mac/MacScrollTypes.h
diff --git a/public/platform/mac/MacScrollTypes.h b/public/platform/mac/MacScrollTypes.h
new file mode 100644
index 0000000000000000000000000000000000000000..2e17df6f0ace27060f719b8e6edaf46c4e64f756
--- /dev/null
+++ b/public/platform/mac/MacScrollTypes.h
@@ -0,0 +1,21 @@
+// Copyright 2015 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.
+
+#ifndef MacScrollTypes_h
+#define MacScrollTypes_h
+
+namespace blink {
+
+enum ScrollbarButtonsPlacement {
+    ScrollbarButtonsNone,

[jochen (gone - plz use gerrit), 2015/07/22 09:52:49]

enum values should start with the name of the enum (i.e.
ScrollbarButtonsPlacementNone). Or use an enum class

[Greg K, 2015/07/22 19:41:55]

Done.

+    ScrollbarButtonsSingle,
+    ScrollbarButtonsDoubleStart,
+    ScrollbarButtonsDoubleEnd,
+    ScrollbarButtonsDoubleBoth,
+    ScrollbarButtonsPlacementLast = ScrollbarButtonsDoubleBoth
+};
+
+}
+
+#endif // MacScrollTypes_h