All graphs for this bug:
  https://chromeperf.appspot.com/group_report?bug_id=831093

(For debugging:) Original alerts at time of bug-filing:
  https://chromeperf.appspot.com/group_report?sid=9f555daaafd07db323897837aafd1fd84e8c695779994b7dd62291f8ca599ad7


Bot(s) for this bug's original alert(s):

chromium-webrtc-rel-7
chromium-webrtc-rel-linux
chromium-webrtc-rel-mac
chromium-webrtc-rel-win10
chromium-webrtc-rel-win8

Using SVC bitrate limits for single layer encoding is what caused this regression.

I've prepared CL which fixes this - https://webrtc-review.googlesource.com/c/src/+/69813

The following revision refers to this bug:
  https://webrtc.googlesource.com/src.git/+/fafeac3517a8c2c702bf3f65dfe4ac0493eb5874

commit fafeac3517a8c2c702bf3f65dfe4ac0493eb5874
Author: Sergey Silkin <ssilkin@webrtc.org>
Date: Fri Apr 13 16:11:18 2018

Use codec's bitrate limits if SVC is off.

Adding SVC rate allocator and layering configurator caused regression
for VP9 non-SVC senders. SVC bitrate limits, which were supposed to
be used only when spatial layering is enabled, are applied when
encoding single spatial layer. E.g. for VP9 360p sender maximum bitrate
is limited to 500kbps.

This fixes the regression. If sender is configured to send VP9 single
layer then codec's bitrate limits are applied to this layer.

Bug:  webrtc:9151 ,  chromium:831093 
Change-Id: Ia1ae4087155ad7917a3443304a21532f1e68ea65
Reviewed-on: https://webrtc-review.googlesource.com/69813
Commit-Queue: Sergey Silkin <ssilkin@webrtc.org>
Reviewed-by: Michael Horowitz <mhoro@webrtc.org>
Reviewed-by: Rasmus Brandt <brandtr@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#22862}
[modify] https://crrev.com/fafeac3517a8c2c702bf3f65dfe4ac0493eb5874/modules/video_coding/codecs/vp9/svc_rate_allocator.cc
[modify] https://crrev.com/fafeac3517a8c2c702bf3f65dfe4ac0493eb5874/modules/video_coding/video_codec_initializer.cc
[modify] https://crrev.com/fafeac3517a8c2c702bf3f65dfe4ac0493eb5874/modules/video_coding/video_codec_initializer_unittest.cc

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/c42eb293fc9fab232250d9550fc37f0677ede892

commit c42eb293fc9fab232250d9550fc37f0677ede892
Author: webrtc-chromium-autoroll@skia-buildbots.google.com.iam.gserviceaccount.com <webrtc-chromium-autoroll@skia-buildbots.google.com.iam.gserviceaccount.com>
Date: Fri Apr 13 23:06:02 2018

Roll src/third_party/webrtc/ 3ef3bfc2a..3acffc3b1 (52 commits)

https://webrtc.googlesource.com/src.git/+log/3ef3bfc2aafa..3acffc3b1668

$ git log 3ef3bfc2a..3acffc3b1 --date=short --no-merges --format='%ad %ae %s'

Created with:
  roll-dep src/third_party/webrtc
BUG= chromium:811683 ,chromium:None,chromium:831093,chromium:None,chromium:None,chromium:b/77825904,chromium:None,chromium:None,chromium:None,chromium:831996,chromium:None,chromium:796112,chromium:None,chromium:None,chromium:None,chromium:None,chromium:None,chromium:None,chromium:None,chromium:None,chromium:None,chromium:None,chromium:None,chromium:827917


The AutoRoll server is located here: https://webrtc-chromium-roll.skia.org

Documentation for the AutoRoller is here:
https://skia.googlesource.com/buildbot/+/master/autoroll/README.md

If the roll is causing failures, please contact the current sheriff, who should
be CC'd on the roll, and stop the roller if necessary.


CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_chromium_archive_rel_ng;master.tryserver.chromium.mac:mac_chromium_archive_rel_ng;master.tryserver.chromium.win:win-msvc-dbg
TBR=webrtc-chromium-sheriffs-robots@google.com

Change-Id: Ib12df502703e5c0d6c0d1dcb935f69f0166fa0be
Reviewed-on: https://chromium-review.googlesource.com/1012762
Commit-Queue: webrtc-chromium-autoroll <webrtc-chromium-autoroll@skia-buildbots.google.com.iam.gserviceaccount.com>
Reviewed-by: webrtc-chromium-autoroll <webrtc-chromium-autoroll@skia-buildbots.google.com.iam.gserviceaccount.com>
Cr-Commit-Position: refs/heads/master@{#550776}
[modify] https://crrev.com/c42eb293fc9fab232250d9550fc37f0677ede892/DEPS

After landing SVC rate allocator we started to apply SVC rate limits even at coding in single layer mode (SVC is off). This has been fixed in https://webrtc-review.googlesource.com/c/src/+/69813.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/c42eb293fc9fab232250d9550fc37f0677ede892

commit c42eb293fc9fab232250d9550fc37f0677ede892
Author: webrtc-chromium-autoroll@skia-buildbots.google.com.iam.gserviceaccount.com <webrtc-chromium-autoroll@skia-buildbots.google.com.iam.gserviceaccount.com>
Date: Fri Apr 13 23:06:02 2018

Roll src/third_party/webrtc/ 3ef3bfc2a..3acffc3b1 (52 commits)

https://webrtc.googlesource.com/src.git/+log/3ef3bfc2aafa..3acffc3b1668

$ git log 3ef3bfc2a..3acffc3b1 --date=short --no-merges --format='%ad %ae %s'

Created with:
  roll-dep src/third_party/webrtc
BUG= chromium:811683 ,chromium:None,chromium:831093,chromium:None,chromium:None,chromium:b/77825904,chromium:None,chromium:None,chromium:None,chromium:831996,chromium:None,chromium:796112,chromium:None,chromium:None,chromium:None,chromium:None,chromium:None,chromium:None,chromium:None,chromium:None,chromium:None,chromium:None,chromium:None,chromium:827917


The AutoRoll server is located here: https://webrtc-chromium-roll.skia.org

Documentation for the AutoRoller is here:
https://skia.googlesource.com/buildbot/+/master/autoroll/README.md

If the roll is causing failures, please contact the current sheriff, who should
be CC'd on the roll, and stop the roller if necessary.


CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_chromium_archive_rel_ng;master.tryserver.chromium.mac:mac_chromium_archive_rel_ng;master.tryserver.chromium.win:win-msvc-dbg
TBR=webrtc-chromium-sheriffs-robots@google.com

Change-Id: Ib12df502703e5c0d6c0d1dcb935f69f0166fa0be
Reviewed-on: https://chromium-review.googlesource.com/1012762
Commit-Queue: webrtc-chromium-autoroll <webrtc-chromium-autoroll@skia-buildbots.google.com.iam.gserviceaccount.com>
Reviewed-by: webrtc-chromium-autoroll <webrtc-chromium-autoroll@skia-buildbots.google.com.iam.gserviceaccount.com>
Cr-Commit-Position: refs/heads/master@{#550776}
[modify] https://crrev.com/c42eb293fc9fab232250d9550fc37f0677ede892/DEPS

The following revision refers to this bug:
  https://webrtc.googlesource.com/src.git/+/ce137ce112e025218a2d266bcfd994bdb5fe4588

commit ce137ce112e025218a2d266bcfd994bdb5fe4588
Author: Sergey Silkin <ssilkin@webrtc.org>
Date: Wed Apr 18 14:59:18 2018

Merge to M67: Use codec's bitrate limits if SVC is off.

Adding SVC rate allocator and layering configurator caused regression
for VP9 non-SVC senders. SVC bitrate limits, which were supposed to
be used only when spatial layering is enabled, are applied when
encoding single spatial layer. E.g. for VP9 360p sender maximum bitrate
is limited to 500kbps.

This fixes the regression. If sender is configured to send VP9 single
layer then codec's bitrate limits are applied to this layer.

(cherry picked from commit fafeac3517a8c2c702bf3f65dfe4ac0493eb5874)

Bug:  chromium:833762 ,  webrtc:9151 ,  chromium:831093 
Change-Id: Ia1ae4087155ad7917a3443304a21532f1e68ea65
Reviewed-on: https://webrtc-review.googlesource.com/70380
Commit-Queue: Sergey Silkin <ssilkin@webrtc.org>
Reviewed-by: Michael Horowitz <mhoro@webrtc.org>
Reviewed-by: Rasmus Brandt <brandtr@webrtc.org>
Cr-Original-Commit-Position: refs/heads/master@{#22862}
Cr-Commit-Position: refs/branch-heads/67@{#2}
Cr-Branched-From: 4da18e89bdee78df4478b66cdd0e6f6a38d61b4d-refs/heads/master@{#22779}
[modify] https://crrev.com/ce137ce112e025218a2d266bcfd994bdb5fe4588/modules/video_coding/codecs/vp9/svc_rate_allocator.cc
[modify] https://crrev.com/ce137ce112e025218a2d266bcfd994bdb5fe4588/modules/video_coding/video_codec_initializer.cc
[modify] https://crrev.com/ce137ce112e025218a2d266bcfd994bdb5fe4588/modules/video_coding/video_codec_initializer_unittest.cc