GitLab

Introduce a queue in TabDelegate for creating multiple Tabs in a row.
This prevents triggering some issue in Android's ActivityManager that
causes it to throw away the tasks for Activities after it launches them,
which in turn causes Android to destroy our Activities.

BUG=498920

Review URL: https://codereview.chromium.org/1229853006

Cr-Commit-Position: refs/heads/master@{#339799}