b=788935 remove unused no-op virtual GLContext::WindowDestroyed() r=vlad

--HG--
extra : rebase_source : ed6bfd166989e0547676916bdf423ca2f4ce7a38

gfx/gl/GLContext.h

@@ -242,8 +242,6 @@ public:
 
     virtual bool SetupLookupFunction() = 0;
 
-    virtual void WindowDestroyed() {}
-
     virtual void ReleaseSurface() {}
 
     void *GetUserData(void *aKey) {