Move JoinString to the base namespace

ui/gl/gl_implementation.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_implementation.h"
 
 #include <algorithm>
 #include <string>
 
 #include "base/at_exit.h"
@@ skipping 155 matching lines @@
   base::SplitString(extensions, ' ', &extension_vec);
 
   auto is_disabled = [&disabled_extensions](const std::string& ext) {
     return std::find(disabled_extensions.begin(), disabled_extensions.end(),
                      ext) != disabled_extensions.end();
   };
   extension_vec.erase(
       std::remove_if(extension_vec.begin(), extension_vec.end(), is_disabled),
       extension_vec.end());
 
-  return JoinString(extension_vec, " ");
+  return base::JoinString(extension_vec, " ");
 }
 
 DisableNullDrawGLBindings::DisableNullDrawGLBindings() {
   initial_enabled_ = SetNullDrawGLBindingsEnabledGL(false);
 }
 
 DisableNullDrawGLBindings::~DisableNullDrawGLBindings() {
   SetNullDrawGLBindingsEnabledGL(initial_enabled_);
 }
 
 GLWindowSystemBindingInfo::GLWindowSystemBindingInfo()
     : direct_rendering(true) {}
 
 }  // namespace gfx