Make sure we have at least two elements in the Map, otherwise we don't
perform a proper dictionary lookup.

Bug: chromium:781218
Change-Id: I471e3822b95c15e3a5b2ac54c8ad1f030bd54d40
Reviewed-on: https://chromium-review.googlesource.com/768708Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
Commit-Queue: Camillo Bruni <cbruni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#49345}