aura/cros: Rename MessagePump{X => AuraX11} and move the atom cache into it.

ui/base/x/events_aurax11.cc

Index: ui/base/x/events_aurax11.cc
diff --git a/ui/base/x/events_x.cc b/ui/base/x/events_aurax11.cc
similarity index 99%
rename from ui/base/x/events_x.cc
rename to ui/base/x/events_aurax11.cc
index f166a8654952fd66f8c1c4264cab349a825c16c3..5a1f0717e6bc2e1537489e974a1d01d522a25373 100644
--- a/ui/base/x/events_x.cc
+++ b/ui/base/x/events_aurax11.cc
@@ -11,7 +11,7 @@
 
 #include "base/command_line.h"
 #include "base/logging.h"
-#include "base/message_pump_x.h"
+#include "base/message_pump_aurax11.h"
 #include "ui/base/keycodes/keyboard_code_conversion_x.h"
 #include "ui/base/ui_base_switches.h"
 #include "ui/base/touch/touch_factory.h"
@@ -559,7 +559,7 @@ float GetTouchParamFromXEvent(XEvent* xev,
 
 Atom GetNoopEventAtom() {
   return XInternAtom(
-      base::MessagePumpX::GetDefaultXDisplay(),
+      base::MessagePumpAuraX11::GetDefaultXDisplay(),
       "noop", False);
 }