aura-x11: Install the dispatcher as a message-pump observer.

ui/aura/root_window_host_linux.cc

Index: ui/aura/root_window_host_linux.cc
diff --git a/ui/aura/root_window_host_linux.cc b/ui/aura/root_window_host_linux.cc
index 4f42775ff14aa9e8c40e44b6a4b72b2f86672dab..dcad33d3dd094e60aa99395dd26cae581da857fd 100644
--- a/ui/aura/root_window_host_linux.cc
+++ b/ui/aura/root_window_host_linux.cc
@@ -47,7 +47,7 @@ const char kRootWindowHostLinuxKey[] = "__AURA_ROOT_WINDOW_HOST_LINUX__";
 // The events reported for slave devices can have incorrect information for some
 // fields. This utility function is used to check for such inconsistencies.
 void CheckXEventForConsistency(XEvent* xevent) {
-#if defined(USE_XI2_MT)
+#if defined(USE_XI2_MT) && !defined(NDEBUG)

[sadrul, 2012/05/16 17:07:01]

I was tempted to just remove this check since we have switched to XI2.2 and the
code it is supposed to check is not used anymore. But I am keeping it only for
debug builds since it has caught event-dispatching bugs in a couple of places,
and may find other such cases.

   static bool expect_master_event = false;
   static XIDeviceEvent slave_event;
   static gfx::Point slave_location;
@@ -92,7 +92,7 @@ void CheckXEventForConsistency(XEvent* xevent) {
     CHECK_EQ(slave_event.mods.locked, xievent->mods.locked);
     CHECK_EQ(slave_event.mods.effective, xievent->mods.effective);
   }
-#endif  // defined(USE_XI2_MT)
+#endif  // defined(USE_XI2_MT) && !defined(NDEBUG)
 }
 
 // Returns X font cursor shape from an Aura cursor.