Make Clipboard::FormatType an opaque handle type.

ui/base/clipboard/scoped_clipboard_writer.cc

Index: ui/base/clipboard/scoped_clipboard_writer.cc
diff --git a/ui/base/clipboard/scoped_clipboard_writer.cc b/ui/base/clipboard/scoped_clipboard_writer.cc
index 9014f3afa9242416b64a73627edad07199038d45..c27567ef8a9c212e9e8c3619b7640c67fd44c1f9 100644
--- a/ui/base/clipboard/scoped_clipboard_writer.cc
+++ b/ui/base/clipboard/scoped_clipboard_writer.cc
@@ -104,9 +104,11 @@ void ScopedClipboardWriter::WriteBitmapFromPixels(const void* pixels,
   objects_[Clipboard::CBF_BITMAP] = parameters;
 }
 
-void ScopedClipboardWriter::WritePickledData(const Pickle& pickle,
-                                             Clipboard::FormatType format) {
-  Clipboard::ObjectMapParam format_parameter(format.begin(), format.end());
+void ScopedClipboardWriter::WritePickledData(
+    const Pickle& pickle, const Clipboard::FormatType& format) {
+  std::string format_string = Clipboard::FormatTypeToString(format);
+  Clipboard::ObjectMapParam format_parameter(format_string.begin(),
+                                             format_string.end());
   Clipboard::ObjectMapParam data_parameter;
 
   data_parameter.resize(pickle.size());