GitLab

The OnSessionRestore callback has been changed to accept the number
of tabs as an argument.

BUG=chromium:455482
TEST=Add logging to make sure the correct number of tabs is being
passed to perf provider during session restore
Signed-off-by: Simon Que <sque@chromium.org>

Review URL: https://codereview.chromium.org/902613003

Cr-Commit-Position: refs/heads/master@{#318168}