GitLab

This way the embedder has a way to persist state with a tab.
Without this the embedder has no way to identify what tab the data
was associated with.

BUG=1056710
TEST=BrowserFragmentLifecycleTests

Change-Id: I944e538ba0110f5d3434d5dfd8aa76fe2fdd08e5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2093691
Commit-Queue: Scott Violet <sky@chromium.org>
Reviewed-by: Evan Stade <estade@chromium.org>
Cr-Commit-Position: refs/heads/master@{#748314}