[Sync] Add tab sync latency UMA

[Sync] Add tab sync latency UMA

Adds a delay measurement before the tab sync data is available to
the chrome://history UI from the time the page is opened.

BUG=476646
Committed: https://crrev.com/d2fe056a75f3a94645b9404d43ecf56f7f2776e6
Cr-Commit-Position: refs/heads/master@{#335075}

[Nicolas Zea, 2015-06-13 00:47:55]

Patchset #2 (id:20001) has been deleted

[Nicolas Zea, 2015-06-13 00:49:26]

zea@chromium.org changed reviewers:
+ asvitkine@chromium.org, bauerb@chromium.org

[Nicolas Zea, 2015-06-13 00:49:27]

+Bernhard for foreign_session_handler, Alexei for histos.

[Bernhard Bauer, 2015-06-15 08:32:45]

lgtm

[Alexei Svitkine (slow), 2015-06-15 14:33:28]

lgtm

https://codereview.chromium.org/1180283002/diff/40001/chrome/browser/ui/webui...
File chrome/browser/ui/webui/foreign_session_handler.cc (right):

https://codereview.chromium.org/1180283002/diff/40001/chrome/browser/ui/webui...
chrome/browser/ui/webui/foreign_session_handler.cc:233: base::Time::Now() -
load_attempt_time_);
Nit: Usually base::TimeTicks:: is used instead - to avoid noise from changes to
system time in-between.

[Nicolas Zea, 2015-06-15 18:01:12]

Thanks!

https://codereview.chromium.org/1180283002/diff/40001/chrome/browser/ui/webui...
File chrome/browser/ui/webui/foreign_session_handler.cc (right):

https://codereview.chromium.org/1180283002/diff/40001/chrome/browser/ui/webui...
chrome/browser/ui/webui/foreign_session_handler.cc:233: base::Time::Now() -
load_attempt_time_);
On 2015/06/15 14:33:28, Alexei Svitkine wrote:
> Nit: Usually base::TimeTicks:: is used instead - to avoid noise from changes
to
> system time in-between.

Done.

[Nicolas Zea, 2015-06-15 18:01:15]

The CQ bit was checked by zea@chromium.org

[Nicolas Zea, 2015-06-15 18:01:16]

The patchset sent to the CQ was uploaded after l-g-t-m from bauerb@chromium.org,
asvitkine@chromium.org
Link to the patchset: https://codereview.chromium.org/1180283002/#ps60001
(title: "Switch to timeticks")

[commit-bot: I haz the power, 2015-06-15 18:02:30]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1180283002/60001

[commit-bot: I haz the power, 2015-06-15 18:20:33]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-06-15 18:20:34]

Try jobs failed on following builders:
  android_chromium_gn_compile_dbg on tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/android_chromiu...)

[Nicolas Zea, 2015-06-17 23:52:50]

The CQ bit was checked by zea@chromium.org

[Nicolas Zea, 2015-06-17 23:52:51]

The patchset sent to the CQ was uploaded after l-g-t-m from bauerb@chromium.org,
asvitkine@chromium.org
Link to the patchset: https://codereview.chromium.org/1180283002/#ps100001
(title: "Fix TimeTicks")

[commit-bot: I haz the power, 2015-06-17 23:56:16]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1180283002/100001

[commit-bot: I haz the power, 2015-06-18 02:02:57]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-06-18 02:02:58]

Try jobs failed on following builders:
  win8_chromium_ng on tryserver.chromium.win (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.win/builders/win8_chromium_ng/...)

[Nicolas Zea, 2015-06-18 17:24:51]

The CQ bit was checked by zea@chromium.org

[commit-bot: I haz the power, 2015-06-18 17:26:41]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1180283002/100001

[commit-bot: I haz the power, 2015-06-18 18:00:17]

Committed patchset #5 (id:100001)

[commit-bot: I haz the power, 2015-06-18 18:01:13]

Patchset 5 (id:??) landed as
https://crrev.com/d2fe056a75f3a94645b9404d43ecf56f7f2776e6
Cr-Commit-Position: refs/heads/master@{#335075}