Fix an issue with GPU stats not enabled

Invoke Surface::enableFrameTimestamps after eglDestroySurface.
eglDestroySurface internally disables time stats. Order is
important, when CanvasContext::setSurface is invoked with
a surface, that is already current (which happens all the time).

Test: ran UiBench microbenchmark tests
Change-Id: I3d023c3a87da6329c556426d553c744e541b9dff