Add another entry to the NoCacheReason enum, reporting that the chromium
ScriptResource has no cache handler.

Also, the amount of chromium-specific entries in this enum is getting
too high. So, added a TODO for removing them -- possibly in the future
we want to do this no-cache reason logging in Chromium after all,
propagating isolate cache hits and consume failures back up the API with
an out parameter.

Bug: chromium:769203
Cq-Include-Trybots: master.tryserver.chromium.linux:linux_chromium_rel_ng
Change-Id: I63ca863cfef61e04e7104318eb79810796b61a9c
Reviewed-on: https://chromium-review.googlesource.com/776893Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/master@{#49458}