This CL changes a constant pool test to include tests for the marker
and the encoded pool size.

Change-Id: Ia5cfd173e5d523a02252fd3b14f302e5c8994881
Reviewed-on: https://chromium-review.googlesource.com/1186626Reviewed-by: Georg Neis <neis@chromium.org>
Commit-Queue: Sigurd Schneider <sigurds@chromium.org>
Cr-Commit-Position: refs/heads/master@{#55423}