GPU: Keep track of the last real context and real surface made current.

ui/gl/gl_context_wgl.h

Index: ui/gl/gl_context_wgl.h
diff --git a/ui/gl/gl_context_wgl.h b/ui/gl/gl_context_wgl.h
index d3f6541ffb0a6b0c9d43195b87a021a241b6c857..13a274be71cd3a19c3dba694d4099790d7ea1691 100644
--- a/ui/gl/gl_context_wgl.h
+++ b/ui/gl/gl_context_wgl.h
@@ -15,7 +15,7 @@ namespace gfx {
 class GLSurface;
 
 // This class is a wrapper around a GL context.
-class GLContextWGL : public GLContext {
+class GLContextWGL : public GLContextReal {
  public:
   explicit GLContextWGL(GLShareGroup* share_group);
   virtual ~GLContextWGL();