Swap-buffers was being deferred (to prevent it being called
from the event handling thread) however when it was called the
OpenGL context might not be active (especially with multiple windows).
Moving the cursor between windows made eglSwapBuffers report:
EGL Error (0x300D): EGL_BAD_SURFACE.
Resolve this by removing swapBuffer calls and instead add a
GHOST_kEventWindowUpdateDecor event intended for redrawing
client-side-decoration.
Besides the warning, this results an error with LIBDECOR window frames
not redrawing when a window became inactive.
721bd5e6cf