They were only limited to 32 bit when using the internal Hashmap. Since
this has changed alreay some time ago, we can switch to 64 bit ids and
check that we never overflow.

Bug: 
Change-Id: Ia6c6d02d6b5e555c6941185a79427dc4aa2a1d62
Reviewed-on: https://chromium-review.googlesource.com/598229
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47085}