Change Clipboard to use virtual methods for testing purposes.

ui/base/clipboard/clipboard.cc

Index: ui/base/clipboard/clipboard.cc
diff --git a/ui/base/clipboard/clipboard.cc b/ui/base/clipboard/clipboard.cc
index 84371acea734acdf5af8947848cb6e320970d617..27f747a048fe4dc7b48309346f3024977bb08c5d 100644
--- a/ui/base/clipboard/clipboard.cc
+++ b/ui/base/clipboard/clipboard.cc
@@ -88,7 +88,7 @@ Clipboard* Clipboard::GetForCurrentThread() {
   if (it != clipboard_map->end())
     return it->second;
 
-  Clipboard* clipboard = new ui::Clipboard;
+  Clipboard* clipboard = Clipboard::Create();
   clipboard_map->insert(std::make_pair(id, clipboard));
   return clipboard;
 }