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

ui/gl/gl_context_osmesa.cc

Index: ui/gl/gl_context_osmesa.cc
diff --git a/ui/gl/gl_context_osmesa.cc b/ui/gl/gl_context_osmesa.cc
index a279177011f7e85c428c8bc4e02088cf9b1292f2..f95a4bd1793cd0666c24e0375588cf2d90294c6d 100644
--- a/ui/gl/gl_context_osmesa.cc
+++ b/ui/gl/gl_context_osmesa.cc
@@ -97,7 +97,7 @@ bool GLContextOSMesa::IsCurrent(GLSurface* surface) {
   // If our context is current then our notion of which GLContext is
   // current must be correct. On the other hand, third-party code
   // using OpenGL might change the current context.
-  DCHECK(!native_context_is_current || (GetCurrent() == this));
+  DCHECK(!native_context_is_current || (GetRealCurrent() == this));
 
   if (!native_context_is_current)
     return false;