Fix hiccups when zooming with a tablet

The hiccups while zooming were happening because of gui controls like
sliders and mode combo box being updated too often during the tablet
stroke.

This patch should also fix the FPS ussies while zooming. Now FPS should
be only limited by the underlying GPU (therefore 60+ FPS).

CCBUG:414576
(cherry picked from commit 4d7f3461458d2608130187fb992797f67a0148fc)