Fix createSurface / eglCreateWindowSurface race.

Previously we could have returned from createSurface on the main thread
before calling eglCreateWindowSurface on the GLThread. That could lead
to a problem because the surface could be destroyed before
eglCreateWindowSurface got a chance to run.

Bug: 8328715
Change-Id: I273149f7d4b165abbe218a91ff54083f3f498cb0