Implement large cursors in Mushrome.

ash/aura/shell_port_classic.cc

Index: ash/aura/shell_port_classic.cc
diff --git a/ash/aura/shell_port_classic.cc b/ash/aura/shell_port_classic.cc
index 105edb5cd79c8202560b19325fea5fa1143a53b8..667b007755de1e52809a42230427a514c1fbccf4 100644
--- a/ash/aura/shell_port_classic.cc
+++ b/ash/aura/shell_port_classic.cc
@@ -85,6 +85,10 @@ void ShellPortClassic::HideCursor() {
   Shell::Get()->cursor_manager()->HideCursor();
 }
 
+void ShellPortClassic::SetCursorSet(ui::CursorSet cursor_set) {
+  Shell::Get()->cursor_manager()->SetCursorSet(cursor_set);
+}
+
 void ShellPortClassic::SetGlobalOverrideCursor(
     base::Optional<ui::CursorData> cursor) {
   // This is part of a fat interface that is only implemented on the mash side;