Or, it might be V4L2_CID_EXPOSURE :-)

https://www.linuxtv.org/downloads/legacy/video4linux/API/V4L2_API/spec-single/v4l2.html#control-id

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/75fdd6023fc3df0feda750ae565f9d663187ae97

commit 75fdd6023fc3df0feda750ae565f9d663187ae97
Author: Miguel Casas-Sanchez <mcasas@chromium.org>
Date: Fri May 19 01:55:29 2017

Image Capture: wire |exposureCompensation| in Linux/CrOs

This CL connects:
- reading of |exposureCompensation| in getPhotoCapabilities() 
- configuring of |exposureCompensation| and |exposureMode| in
setPhotoOptions().

Bug:  723930 
Change-Id: Ib3ceeacf1df34722fd274ebe935a1c890ae0c4c2
Reviewed-on: https://chromium-review.googlesource.com/508415
Reviewed-by: Reilly Grant <reillyg@chromium.org>
Commit-Queue: Miguel Casas <mcasas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#473027}
[modify] https://crrev.com/75fdd6023fc3df0feda750ae565f9d663187ae97/media/capture/video/linux/v4l2_capture_delegate.cc

Your change meets the bar and is auto-approved for M59. Please go ahead and merge the CL to branch 3071 manually. Please contact milestone owner if you have questions.
Owners: amineer@(Android), cmasso@(iOS), gkihumba@(ChromeOS), Abdul Syed@(Desktop)

For more details visit https://www.chromium.org/issue-tracking/autotriage - Your friendly Sheriffbot

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/d0254e8a8367112742a55bca64347a6b8cd83ec1

commit d0254e8a8367112742a55bca64347a6b8cd83ec1
Author: Miguel Casas-Sanchez <mcasas@chromium.org>
Date: Sat May 20 02:27:42 2017

Image Capture: wire |exposureCompensation| in Linux/CrOs

This CL connects:
- reading of |exposureCompensation| in getPhotoCapabilities()
- configuring of |exposureCompensation| and |exposureMode| in
setPhotoOptions().

Bug:  723930 
Change-Id: Ib3ceeacf1df34722fd274ebe935a1c890ae0c4c2
Reviewed-on: https://chromium-review.googlesource.com/508415
Reviewed-by: Reilly Grant <reillyg@chromium.org>
Commit-Queue: Miguel Casas <mcasas@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#473027}
Review-Url: https://codereview.chromium.org/2890353003 .
Cr-Commit-Position: refs/branch-heads/3071@{#643}
Cr-Branched-From: a106f0abbf69dad349d4aaf4bcc4f5d376dd2377-refs/heads/master@{#464641}

[modify] https://crrev.com/d0254e8a8367112742a55bca64347a6b8cd83ec1/media/capture/video/linux/v4l2_capture_delegate.cc

On my Chromebook Pixel with Chrome 60.0.3105.0 (Official Build) canary (64-bit),
I get exposureCompensation: { min: 4, max: 1250, step: 1 }

However, the only options that update (visually at least) the current camera stream are:

4 -> 84
100
200
300 
598
1195


For info, v4l2-ctl returns:

  exposure_absolute (int)    : min=4 max=1250 step=1 default=166 value=4

Here's the full log of v4l2-ctl:

                     brightness (int)    : min=0 max=255 step=1 default=128 value=128
                       contrast (int)    : min=0 max=255 step=1 default=32 value=32
                     saturation (int)    : min=0 max=100 step=1 default=64 value=64
                            hue (int)    : min=-180 max=180 step=1 default=0 value=0
 white_balance_temperature_auto (bool)   : default=1 value=1
                          gamma (int)    : min=90 max=150 step=1 default=120 value=120
           power_line_frequency (menu)   : min=0 max=2 default=1 value=1
      white_balance_temperature (int)    : min=2800 max=6500 step=1 default=4000 value=4000 flags=inactive
                      sharpness (int)    : min=0 max=7 step=1 default=2 value=2
         backlight_compensation (int)    : min=0 max=2 step=1 default=1 value=1
                  exposure_auto (menu)   : min=0 max=3 default=3 value=1
              exposure_absolute (int)    : min=4 max=1250 step=1 default=166 value=4
         exposure_auto_priority (bool)   : default=0 value=1

#10 yep I saw the same effects, seems like the upper ranges
are meant for very bright (or dark, not quite sure) scenes.