Change X11 error handler override to allow easy X11 error checking.

ui/base/x/x11_util_internal.h

Index: ui/base/x/x11_util_internal.h
diff --git a/ui/base/x/x11_util_internal.h b/ui/base/x/x11_util_internal.h
index 70eb088c786e8668e48eb2f65f14f0d0a425a423..46f1d7cebbd3fad5210aa65fe821388581badd16 100644
--- a/ui/base/x/x11_util_internal.h
+++ b/ui/base/x/x11_util_internal.h
@@ -14,6 +14,7 @@
 
 extern "C" {
 #include <X11/Xatom.h>
+#include <X11/Xdefs.h>
 #include <X11/Xlib.h>
 #include <X11/extensions/XShm.h>
 #include <X11/extensions/Xrender.h>
@@ -50,6 +51,10 @@ UI_EXPORT void SetX11ErrorHandlers(XErrorHandler error_handler,
 UI_EXPORT void LogErrorEventDescription(Display* dpy,
                                         const XErrorEvent& error_event);
 
+// Returns the last X11 error encountered and clears it. Calls XSync to ensure
+// all requests have been received and processed by the X server.

[Ami GONE FROM CHROMIUM, 2011/09/14 23:23:11]

Document semantics of NULL return.

[Ami GONE FROM CHROMIUM, 2011/09/14 23:23:11]

If you really returned a pointer here you'd want you to doco the ownership
semantics of it (but see .cc commentary).

+UI_EXPORT XErrorEvent* GetLastX11Error(Display* display);

[Ami GONE FROM CHROMIUM, 2011/09/14 23:23:11]

s/Get/GetAndClear/

[Ami GONE FROM CHROMIUM, 2011/09/14 23:23:11]

I wonder about the threading semantics here.  Do you not need to restrict
callers to the thread dealing w/ xlib?
(xlib is thread-unsafe)

+
 }  // namespace ui
 
 #endif  // UI_BASE_X_X11_UTIL_INTERNAL_H_