[Offline Pages] Adds UMA for number of started attempts and for network

[Offline Pages] Adds UMA for number of started attempts and for network
connection when Unsupported Scheme error encountered.

These changes are a follow-up to bug 642025 and the patch landed to
mitigate it. They are meant to give us more visibility for tuning the
policy for max number of started attempts for a request and whether we
might use the network connection to better understand the nature of
the Unsupported Scheme error.

Also this reduces the max number of start attempts from 5 to 4. I
tried 2 EM URLs that took 3 attempts on GIN-2g on GIN-2g-poor and one
took only 2 attempts while the other took 4 attempts so I don't want
to lower this too much yet (and see what new UMA reveals).

BUG=642923
Review-Url: https://codereview.chromium.org/2301703002
Cr-Commit-Position: refs/heads/master@{#416101}
(cherry picked from commit 22647f96af79fb0d563644640689a8fc678f15ac)

Committed: https://chromium.googlesource.com/chromium/src/+/8d69874fb6de3c8c2e688cd264c416bb2c0fc906

[Pete Williamson, 2016-09-06 21:01:42]

Description was changed from

==========
[Offline Pages] Adds UMA for number of started attempts and for network
connection when Unsupported Scheme error encountered.

These changes are a follow-up to bug 642025 and the patch landed to
mitigate it. They are meant to give us more visibility for tuning the
policy for max number of started attempts for a request and whether we
might use the network connection to better understand the nature of
the Unsupported Scheme error.

Also this reduces the max number of start attempts from 5 to 4. I
tried 2 EM URLs that took 3 attempts on GIN-2g on GIN-2g-poor and one
took only 2 attempts while the other took 4 attempts so I don't want
to lower this too much yet (and see what new UMA reveals).

BUG=642923

Review-Url: https://codereview.chromium.org/2301703002
Cr-Commit-Position: refs/heads/master@{#416101}
(cherry picked from commit 22647f96af79fb0d563644640689a8fc678f15ac)
==========

to

==========
[Offline Pages] Adds UMA for number of started attempts and for network
connection when Unsupported Scheme error encountered.

These changes are a follow-up to bug 642025 and the patch landed to
mitigate it. They are meant to give us more visibility for tuning the
policy for max number of started attempts for a request and whether we
might use the network connection to better understand the nature of
the Unsupported Scheme error.

Also this reduces the max number of start attempts from 5 to 4. I
tried 2 EM URLs that took 3 attempts on GIN-2g on GIN-2g-poor and one
took only 2 attempts while the other took 4 attempts so I don't want
to lower this too much yet (and see what new UMA reveals).

BUG=642923

Review-Url: https://codereview.chromium.org/2301703002
Cr-Commit-Position: refs/heads/master@{#416101}
(cherry picked from commit 22647f96af79fb0d563644640689a8fc678f15ac)

Committed:
https://chromium.googlesource.com/chromium/src/+/8d69874fb6de3c8c2e688cd264c4...
==========

[Pete Williamson, 2016-09-06 21:01:44]

Committed patchset #1 (id:1) manually as
8d69874fb6de3c8c2e688cd264c416bb2c0fc906.