The http/tests/devtools/layers and agents-enable-disable.js failures were fixed in:
https://chromium.googlesource.com/chromium/src/+/1743273d0ea5d0d73e4ba5cbdc1c9acb684e21ff

The devtools/tracing/timeline-paint failures have been pulled off into  https://crbug.com/789184 .

That leaves the following tests that still need investigation:
http/tests/devtools/device-mode/default-background-color.html
http/tests/devtools/layers/layer-compositing-reasons.js
http/tests/devtools/layers/layer-tree-model.js

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/122fa6560e0c8cb675fc32045805e65d53f03a6e

commit 122fa6560e0c8cb675fc32045805e65d53f03a6e
Author: Philip Rogers <pdr@chromium.org>
Date: Wed Dec 06 00:33:55 2017

[root layer scrolls] Rebaseline devtools layer tree and compositing test

layer-tree-model.js:
This test dumps the layer tree and associated elements. With root
layer scrolling (RLS), the layers are associated with different
elements (e.g., the iframe scrolling contents layer is "#document"
instead of "iframe#frame") and there are a different number of
layers, but the test passes otherwise.

layer-compositing-reasons.js:
This test dumps the compositing reasons for all layers, directly from
the GraphicsLayer object. With RLS, the root layer has two additional
reasons: overflowScrollingTouch and rootScroller.

Bug:  781428 
Change-Id: Ibc1e654474c96d2dd8dfdfc01ec52046989c30cb
Cq-Include-Trybots: master.tryserver.chromium.linux:linux_layout_tests_root_layer_scrolls
Reviewed-on: https://chromium-review.googlesource.com/804620
Commit-Queue: Philip Rogers <pdr@chromium.org>
Reviewed-by: Stefan Zager <szager@chromium.org>
Cr-Commit-Position: refs/heads/master@{#521914}
[modify] https://crrev.com/122fa6560e0c8cb675fc32045805e65d53f03a6e/third_party/WebKit/LayoutTests/FlagExpectations/root-layer-scrolls
[add] https://crrev.com/122fa6560e0c8cb675fc32045805e65d53f03a6e/third_party/WebKit/LayoutTests/flag-specific/root-layer-scrolls/http/tests/devtools/layers/layer-compositing-reasons-expected.txt
[add] https://crrev.com/122fa6560e0c8cb675fc32045805e65d53f03a6e/third_party/WebKit/LayoutTests/flag-specific/root-layer-scrolls/http/tests/devtools/layers/layer-tree-model-expected.txt
[modify] https://crrev.com/122fa6560e0c8cb675fc32045805e65d53f03a6e/third_party/WebKit/LayoutTests/http/tests/devtools/layers/layer-tree-model.js

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/8628e5bedc0375b0faa54e6aebf03c01661381bc

commit 8628e5bedc0375b0faa54e6aebf03c01661381bc
Author: Philip Rogers <pdr@chromium.org>
Date: Wed Dec 06 04:01:49 2017

[root layer scrolls] Repaint scrolling on bg color override change

This patch ensures the scrolling contents layer is repainted when
the background color is changed with the inspector protocol.

Bug:  781428 
Change-Id: Ia7ba3e7acdf55bf557e42cd9fab62d08f2ce3a0c
Cq-Include-Trybots: master.tryserver.chromium.linux:linux_layout_tests_root_layer_scrolls
Reviewed-on: https://chromium-review.googlesource.com/805006
Commit-Queue: Philip Rogers <pdr@chromium.org>
Reviewed-by: Stefan Zager <szager@chromium.org>
Cr-Commit-Position: refs/heads/master@{#521996}
[modify] https://crrev.com/8628e5bedc0375b0faa54e6aebf03c01661381bc/third_party/WebKit/LayoutTests/FlagExpectations/root-layer-scrolls
[modify] https://crrev.com/8628e5bedc0375b0faa54e6aebf03c01661381bc/third_party/WebKit/Source/core/frame/LocalFrameView.cpp

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/5b066b1e5e0daab9f6e73da0b09660827749a24f

commit 5b066b1e5e0daab9f6e73da0b09660827749a24f
Author: Philip Rogers <pdr@chromium.org>
Date: Wed Feb 28 19:29:54 2018

[RLS] Mark text-editor-formatter.js as not timing out on Win

text-editor-formatter.js is no longer timing out on windows:
https://test-results.appspot.com/dashboards/flakiness_dashboard.html#testType=webkit_layout_tests&tests=http%2Ftests%2Fdevtools%2Feditor%2Ftext-editor-formatter.js

While slow, the slowest run is 5s which is equal to the slowest mac
run. This patch removes the timeout expectation.

Bug:  781428 
Change-Id: I707171e7a32224dc915570e692d33bf86d08d120
Reviewed-on: https://chromium-review.googlesource.com/941409
Reviewed-by: Steve Kobes <skobes@chromium.org>
Commit-Queue: Philip Rogers <pdr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#539921}
[modify] https://crrev.com/5b066b1e5e0daab9f6e73da0b09660827749a24f/third_party/WebKit/LayoutTests/TestExpectations

There's no devtools tests remaining for RLS in TestExpectations so this is fixed. Good job team.