The test is enhanced to perform the copy multiple times.  Initially, the
copy creates a new texture from a 16x16 framebuffer.  Then, a copy is
made from another 16x16 framebuffer (which should not trigger the
recreation of the texture).  Finally, a copy is made from a 32x32
framebuffer (which should trigger the recreation of the texture).

Bug: angleproject:2958
Change-Id: Idc934d6f3d6312a2122d079309a4c2ae2608ba7f
Reviewed-on: https://chromium-review.googlesource.com/c/1392388Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>