Re-land: cc: Fail more visibly when sync queries are not working correctly.

Re-land: cc: Fail more visibly when sync queries are not working correctly.

Instead of creating an infinite number of sync queries, which will
eventually cause performance issues, log an error message and block
until oldest query has passed when reaching 16 pending queries.

BUG=371530, 373360
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=273255

[piman, 2014-05-12 19:41:08]

lgtm

[reveman, 2014-05-12 21:00:16]

The CQ bit was checked by reveman@chromium.org

[commit-bot: I haz the power, 2014-05-12 21:01:27]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/reveman@chromium.org/280543003/1

[commit-bot: I haz the power, 2014-05-13 00:34:17]

FYI, CQ is re-trying this CL (attempt #1).
Please consider checking whether the failures are real,
and report flakes to chrome-troopers@google.com.
The failing builders are:
  android_aosp on tryserver.chromium
(http://build.chromium.org/p/tryserver.chromium/builders/android_aosp/builds/7...)
  android_dbg on tryserver.chromium
(http://build.chromium.org/p/tryserver.chromium/builders/android_dbg/builds/18...)
  linux_chromium_chromeos_rel on tryserver.chromium
(http://build.chromium.org/p/tryserver.chromium/builders/linux_chromium_chrome...)
  linux_chromium_rel on tryserver.chromium
(http://build.chromium.org/p/tryserver.chromium/builders/linux_chromium_rel/bu...)

[commit-bot: I haz the power, 2014-05-13 00:48:36]

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

[commit-bot: I haz the power, 2014-05-13 00:48:37]

Try jobs failed on following builders:
  android_dbg on tryserver.chromium
(http://build.chromium.org/p/tryserver.chromium/builders/android_dbg/builds/18...)

[reveman, 2014-05-13 15:52:11]

The CQ bit was checked by reveman@chromium.org

[commit-bot: I haz the power, 2014-05-13 15:52:24]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/reveman@chromium.org/280543003/20001

[commit-bot: I haz the power, 2014-05-13 18:54:55]

FYI, CQ is re-trying this CL (attempt #1).
Please consider checking whether the failures are real,
and report flakes to chrome-troopers@google.com.
The failing builders are:
  win_chromium_rel on tryserver.chromium
(http://build.chromium.org/p/tryserver.chromium/builders/win_chromium_rel/buil...)

[commit-bot: I haz the power, 2014-05-13 22:11:27]

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

[commit-bot: I haz the power, 2014-05-13 22:11:28]

Try jobs failed on following builders:
  win_chromium_rel on tryserver.chromium
(http://build.chromium.org/p/tryserver.chromium/builders/win_chromium_rel/buil...)

[reveman, 2014-05-13 22:14:03]

The CQ bit was checked by reveman@chromium.org

[commit-bot: I haz the power, 2014-05-13 22:14:58]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/reveman@chromium.org/280543003/20001

[commit-bot: I haz the power, 2014-05-14 00:26:45]

Change committed as 270265

[reveman, 2014-05-23 18:26:11]

The CQ bit was checked by reveman@chromium.org

[commit-bot: I haz the power, 2014-05-23 18:26:48]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/reveman@chromium.org/280543003/20001

[commit-bot: I haz the power, 2014-05-23 18:28:52]

Change committed as 272565

[reveman, 2014-05-28 15:58:15]

The CQ bit was checked by reveman@chromium.org

[commit-bot: I haz the power, 2014-05-28 15:59:52]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/reveman@chromium.org/280543003/20001

[commit-bot: I haz the power, 2014-05-28 16:01:51]

Change committed as 273255