For a single deferred commands, using a jump table is overkill, so
instead simply test the token against the single entry.

Bug: v8:4280
Bug: v8:6218
Change-Id: I0300f640080705fb10f46ad4ed5791703fa4dd77
Reviewed-on: https://chromium-review.googlesource.com/506153
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#45393}