ui: Enable virtual contexts for linux

ui/gl/gl_surface_glx.h

 // 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.
 
 #ifndef UI_GL_GL_SURFACE_GLX_H_
 #define UI_GL_GL_SURFACE_GLX_H_
 
 #include <string>
 
 #include "base/compiler_specific.h"
@@ skipping 26 matching lines @@
 
   void* GetDisplay() override;
 
   // Get the FB config that the surface was created with or NULL if it is not
   // a GLX drawable.
   void* GetConfig() override = 0;
 
  protected:
   ~GLSurfaceGLX() override;
 
+  static void* GetConfig(gfx::AcceleratedWidget window);
+
  private:
   DISALLOW_COPY_AND_ASSIGN(GLSurfaceGLX);
 };
 
 // A surface used to render to a view.
 class GL_EXPORT NativeViewGLSurfaceGLX : public GLSurfaceGLX,
                                          public ui::PlatformEventDispatcher {
  public:
   explicit NativeViewGLSurfaceGLX(gfx::AcceleratedWidget window);
 
@@ skipping 29 matching lines @@
 
   void* config_;
   gfx::Size size_;
 
   scoped_ptr<VSyncProvider> vsync_provider_;
 
   DISALLOW_COPY_AND_ASSIGN(NativeViewGLSurfaceGLX);
 };
 
 // A surface used to render to an offscreen pbuffer.
-class GL_EXPORT PbufferGLSurfaceGLX : public GLSurfaceGLX {
+class GL_EXPORT UnmappedNativeViewGLSurfaceGLX : public GLSurfaceGLX {
  public:
-  explicit PbufferGLSurfaceGLX(const gfx::Size& size);
+  explicit UnmappedNativeViewGLSurfaceGLX(const gfx::Size& size);
 
   // Implement GLSurfaceGLX.
   bool Initialize() override;
   void Destroy() override;
   bool IsOffscreen() override;
   bool SwapBuffers() override;
   gfx::Size GetSize() override;
   void* GetHandle() override;
   void* GetConfig() override;
 
  protected:
-  ~PbufferGLSurfaceGLX() override;
+  ~UnmappedNativeViewGLSurfaceGLX() override;
 
  private:
   gfx::Size size_;
   void* config_;
-  XID pbuffer_;
+  // Unmapped dummy window, used to provide a compatible surface.
+  gfx::AcceleratedWidget window_;
 
-  DISALLOW_COPY_AND_ASSIGN(PbufferGLSurfaceGLX);
+  DISALLOW_COPY_AND_ASSIGN(UnmappedNativeViewGLSurfaceGLX);
 };
 
 }  // namespace gfx
 
 #endif  // UI_GL_GL_SURFACE_GLX_H_