Fix incorrect InterframeDelayMaxInMs histogram metrics

Fix incorrect InterframeDelayMaxInMs histogram metrics

Two bugs:

1) The max value should only be reported if the average is also
   reported. Otherwise the max might become lower than average.
   (On average).

2) When reporting that max value, actually use the max value.

BUG=webrtc:7420
Review-Url: https://codereview.webrtc.org/3002593002
Cr-Commit-Position: refs/heads/master@{#19352}
Committed: https://chromium.googlesource.com/external/webrtc/+/892dab52b6436ce00f508726729eded75a25503d

[sprang_webrtc, 2017-08-14 15:33:01]

sprang@webrtc.org changed reviewers:
+ philipel@webrtc.org

[philipel, 2017-08-15 10:37:56]

lgtm

[sprang_webrtc, 2017-08-15 11:06:50]

The CQ bit was checked by sprang@webrtc.org

[commit-bot: I haz the power, 2017-08-15 11:07:02]

CQ is trying da patch.

Follow status at:
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.webrtc.org/...

[commit-bot: I haz the power, 2017-08-15 12:00:34]

CQ is committing da patch.

Bot data: {"patchset_id": 1, "attempt_start_ts": 1502795210744730, "parent_rev":
"b5ed905ce78334bbeb7b40f58bcd1ec455cca7a3", "commit_rev":
"892dab52b6436ce00f508726729eded75a25503d"}

[commit-bot: I haz the power, 2017-08-15 12:00:38]

Description was changed from

==========
Fix incorrect InterframeDelayMaxInMs histogram metrics

Two bugs:

1) The max value should only be reported if the average is also
   reported. Otherwise the max might become lower than average.
   (On average).

2) When reporting that max value, actually use the max value.

BUG=webrtc:7420
==========

to

==========
Fix incorrect InterframeDelayMaxInMs histogram metrics

Two bugs:

1) The max value should only be reported if the average is also
   reported. Otherwise the max might become lower than average.
   (On average).

2) When reporting that max value, actually use the max value.

BUG=webrtc:7420

Review-Url: https://codereview.webrtc.org/3002593002
Cr-Commit-Position: refs/heads/master@{#19352}
Committed:
https://chromium.googlesource.com/external/webrtc/+/892dab52b6436ce00f5087267...
==========

[commit-bot: I haz the power, 2017-08-15 12:00:39]

Committed patchset #1 (id:1) as
https://chromium.googlesource.com/external/webrtc/+/892dab52b6436ce00f5087267...