x11: Remove MessagePumpObserver.

Convert the last ramining instances of MessagePumpObservers into
PlatformEventObservers, and remove support for MessagePumpObservers
from non-Windows platforms.

BUG=354062
R=sky@chromium.org
TBR=darin@chromium.org

Review URL: https://codereview.chromium.org/233653002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@263158 0039d316-1c4b-4281-b951-d872f2087c98


CrOS-Libchrome-Original-Commit: e10f5fe11f4e034f7e12bd5cf4ab0a9d11bb8639
diff --git a/base/message_loop/message_loop.h b/base/message_loop/message_loop.h
index a56de80..6539c65 100644
--- a/base/message_loop/message_loop.h
+++ b/base/message_loop/message_loop.h
@@ -93,8 +93,7 @@
 //
 class BASE_EXPORT MessageLoop : public MessagePump::Delegate {
  public:
-
-#if defined(USE_AURA)
+#if defined(OS_WIN)
   typedef MessagePumpObserver Observer;
 #elif defined(USE_GTK_MESSAGE_PUMP)
   typedef MessagePumpGdkObserver Observer;
@@ -577,10 +576,8 @@
   void Start();
 #endif
 
-#if !defined(OS_NACL) && (defined(TOOLKIT_GTK) || \
-                          defined(OS_WIN) || defined(USE_X11))
-  // Please see message_pump_win/message_pump_glib for definitions of these
-  // methods.
+#if !defined(OS_NACL) && defined(OS_WIN)
+  // Please see message_pump_win for definitions of these methods.
   void AddObserver(Observer* observer);
   void RemoveObserver(Observer* observer);
 #endif