On Android Adreno eglMakeCurrent resets TransformFeedback position.
Workaround is to pause TransformFeedback before eglMakeCurrent
and resume afterwards.

BUG=angleproject:1426
TEST=TransformFeedbackTest.MultiContext

Change-Id: I4fdb9edbd28b4b16c01d1a94419e78160b31b79f
Reviewed-on: https://chromium-review.googlesource.com/355676Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>
Commit-Queue: Yuly Novikov <ynovikov@chromium.org>