Are you actively working on this? thanhph@ was thinking of picking this up.

No, I'm not working on this at the moment, I guess I ended up being assignee because I've worked on screenshots in DevTools. Handing over to thanhph@, please feel free to ping me if you need any help on part of DevTools.

Any update on this?

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/2acabd1217dd8ca92fb3269e7be7619ef77ca5a0

commit 2acabd1217dd8ca92fb3269e7be7619ef77ca5a0
Author: Saman Sami <samans@chromium.org>
Date: Sat Mar 10 00:51:09 2018

Use FrameSinkVideoCapturer in DevTools eyedropper tool

The eyedropper tool currently depends on being notified about arrival
of CompositorFrames from the renderer which is incompatible with the
VizDisplayCompositor feature. If viz is enabled, use the new video
capture API with is compatible with viz.

TBR=jam@chromium.org

Bug:  771336 
Change-Id: I3e0edaf9cc467045a00fa05212ce79cfd58065c9
Reviewed-on: https://chromium-review.googlesource.com/949885
Commit-Queue: Saman Sami <samans@chromium.org>
Reviewed-by: John Rummell <jrummell@chromium.org>
Reviewed-by: Andrey Kosyakov <caseq@chromium.org>
Reviewed-by: Yuri Wiitala <miu@chromium.org>
Reviewed-by: Antoine Labour <piman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#542299}
[modify] https://crrev.com/2acabd1217dd8ca92fb3269e7be7619ef77ca5a0/chrome/browser/DEPS
[modify] https://crrev.com/2acabd1217dd8ca92fb3269e7be7619ef77ca5a0/chrome/browser/devtools/BUILD.gn
[modify] https://crrev.com/2acabd1217dd8ca92fb3269e7be7619ef77ca5a0/chrome/browser/devtools/devtools_eye_dropper.cc
[modify] https://crrev.com/2acabd1217dd8ca92fb3269e7be7619ef77ca5a0/chrome/browser/devtools/devtools_eye_dropper.h
[modify] https://crrev.com/2acabd1217dd8ca92fb3269e7be7619ef77ca5a0/content/browser/renderer_host/render_widget_host_view_base.cc
[modify] https://crrev.com/2acabd1217dd8ca92fb3269e7be7619ef77ca5a0/content/browser/renderer_host/render_widget_host_view_base.h
[modify] https://crrev.com/2acabd1217dd8ca92fb3269e7be7619ef77ca5a0/content/public/browser/render_widget_host_view.h

We have already implemented a new code path that doesn't rely on CompositorFrameMetadata. I just need to remove the old code path once we hit stable.