gpu: Fix corrupted state due to virtual MakeCurrent race.

ui/gl/gl_gl_api_implementation.cc

Index: ui/gl/gl_gl_api_implementation.cc
diff --git a/ui/gl/gl_gl_api_implementation.cc b/ui/gl/gl_gl_api_implementation.cc
index 1002dbd278842f0e51a8868f58b1bea16bf5f5fe..6aa521689bacb148fd7f05b4c5f0b9f37d206641 100644
--- a/ui/gl/gl_gl_api_implementation.cc
+++ b/ui/gl/gl_gl_api_implementation.cc
@@ -251,6 +251,12 @@ void VirtualGLApi::Initialize(DriverGL* driver, GLContext* real_context) {
 }
 
 bool VirtualGLApi::MakeCurrent(GLContext* virtual_context, GLSurface* surface) {
+  DCHECK_EQ(!virtual_context, !surface);
+  if (!virtual_context && !surface) {
+    current_context_ = NULL;
+    return true;
+  }
+
   bool switched_contexts = g_current_gl_context != this;
   GLSurface* current_surface = GLSurface::GetCurrent();
   if (switched_contexts || surface != current_surface) {