gl: Move platform-specific EGL code into separate files

ui/gl/gl_surface_osmesa.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 "base/logging.h"
+#include "third_party/mesa/src/include/GL/osmesa.h"
 #include "ui/gl/gl_bindings.h"
 #include "ui/gl/gl_context.h"
 #include "ui/gl/gl_surface_osmesa.h"
 #include "ui/gl/scoped_make_current.h"
 
 namespace gfx {
 
 GLSurfaceOSMesa::GLSurfaceOSMesa(unsigned format, const gfx::Size& size)
     : format_(format),
       size_(size) {
@@ skipping 59 matching lines @@
 }
 
 unsigned GLSurfaceOSMesa::GetFormat() {
   return format_;
 }
 
 GLSurfaceOSMesa::~GLSurfaceOSMesa() {
   Destroy();
 }
 
+bool GLSurfaceOSMesaHeadless::IsOffscreen() { return false; }
+
+bool GLSurfaceOSMesaHeadless::SwapBuffers() { return true; }
+
+GLSurfaceOSMesaHeadless::GLSurfaceOSMesaHeadless()
+    : GLSurfaceOSMesa(OSMESA_BGRA, gfx::Size(1, 1)) {}
+
+GLSurfaceOSMesaHeadless::~GLSurfaceOSMesaHeadless() { Destroy(); }
+
 }  // namespace gfx