Fix xcb crash when creating gl context

ui/gl/gl_context_glx.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/gl/gl_context_glx.h"
 
 extern "C" {
 #include <X11/Xlib.h>
 }
 #include <memory>
@@ skipping 39 matching lines @@
   if (profile_mask != 0 && GLSurfaceGLX::IsCreateContextProfileSupported()) {
     attribs.push_back(GLX_CONTEXT_PROFILE_MASK_ARB);
     attribs.push_back(profile_mask);
   }
 
   attribs.push_back(0);
 
   // When creating a context with glXCreateContextAttribsARB, a variety of X11
   // errors can be generated. To prevent these errors from crashing our process,
   // we simply ignore them and only look if the GLXContext was created.
+  // Sync to ensure any errors generated are processed.
+  XSync(display, False);
   auto old_error_handler = XSetErrorHandler(IgnoreX11Errors);
   GLXContext context =
       glXCreateContextAttribsARB(display, config, share, True, attribs.data());
   XSetErrorHandler(old_error_handler);
 
   return context;
 }
 
 GLXContext CreateHighestVersionContext(Display* display,
                                        GLXFBConfig config,
@@ skipping 240 matching lines @@
 
 bool GLContextGLX::WasAllocatedUsingRobustnessExtension() {
   return GLSurfaceGLX::IsCreateContextRobustnessSupported();
 }
 
 GLContextGLX::~GLContextGLX() {
   Destroy();
 }
 
 }  // namespace gl