Linux: include system Mesa headers when using system Mesa.

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.
 
 extern "C" {
 #include <X11/Xlib.h>
 }
 
 #include "ui/gl/gl_context_glx.h"
 
 #include "base/debug/trace_event.h"
 #include "base/logging.h"
 #include "base/memory/scoped_ptr.h"
-#include "third_party/mesa/MesaLib/include/GL/osmesa.h"
+#include "third_party/mesa/include/osmesa.h"
 #include "ui/gl/gl_bindings.h"
 #include "ui/gl/gl_implementation.h"
 #include "ui/gl/gl_surface_glx.h"
 
 namespace gfx {
 
 namespace {
 
 // scoped_ptr functor for XFree(). Use as follows:
 //   scoped_ptr_malloc<XVisualInfo, ScopedPtrXFree> foo(...);
@@ skipping 236 matching lines @@
 
 bool GLContextGLX::WasAllocatedUsingRobustnessExtension() {
   return GLSurfaceGLX::IsCreateContextRobustnessSupported();
 }
 
 GLContextGLX::~GLContextGLX() {
   Destroy();
 }
 
 }  // namespace gfx