Bug 1656853 - Check for EGL context to be alive on destruction r=aosmond,jgilbert

This probably doesn't matter, as the changes will be rolled back by
https://phabricator.services.mozilla.com/D85496
But the change should fix the crash anyway, for now.

Differential Revision: https://phabricator.services.mozilla.com/D86069

gfx/gl/GLContextProviderEGL.cpp

@@ -392,7 +392,7 @@ GLContextEGL::~GLContextEGL() {
   MarkDestroyed();
 
   // Wrapped context should not destroy eglContext/Surface
-  if (!mOwnsContext) {
+  if (!mOwnsContext || !mEgl->IsAlive()) {
     return;
   }