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As requested by Drive SRE these changes reduce the frequency of requests on the
drive back ends, and also lessens the likelihood of convoying.

1. When XMPP is connected, change the poll timeout for changes from 5 minutes to
   between 60 & 120 minutes.
2. When XMPP is disconnected, change the poll timeout for changes from 1 minute
   to between 1 and 2 minutes. This issues start page token requests which are
   cheap for the drive back ends.
3. When batching XMPP notifications, change the batch time from 5 seconds to
   between 15 and 30 seconds. This reduces the QPS on drive back ends when a
   team drive change notification is broadcast to a large corpus of users, and
   prevents convoying of requests by introducing jitter.

Bug: 905201
Change-Id: I5310d956c9ccb5b59261cdf99bbefb515f75771f
Reviewed-on: https://chromium-review.googlesource.com/c/1336949Reviewed-by: Sam McNally <sammc@chromium.org>
Commit-Queue: Stuart Langley <slangley@chromium.org>
Cr-Commit-Position: refs/heads/master@{#608239}