Version 57.0.2976.5 canary (64-bit)

For me it's only if debug tools is detached to a separate window.
Then device mode does not show on page, if i attach it to bottom device mode shows.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/cf853f861018bf40bb283f50f12cade69db0091e

commit cf853f861018bf40bb283f50f12cade69db0091e
Author: pfeldman <pfeldman@chromium.org>
Date: Tue Jan 10 19:16:37 2017

DevTools: extract the dom_extension module.

BUG= 679551 

Review-Url: https://codereview.chromium.org/2620823002
Cr-Commit-Position: refs/heads/master@{#442651}

[modify] https://crrev.com/cf853f861018bf40bb283f50f12cade69db0091e/third_party/WebKit/LayoutTests/inspector/initial-modules-load-expected.txt
[modify] https://crrev.com/cf853f861018bf40bb283f50f12cade69db0091e/third_party/WebKit/LayoutTests/inspector/open-with-rendering-option-enabled-expected.txt
[modify] https://crrev.com/cf853f861018bf40bb283f50f12cade69db0091e/third_party/WebKit/Source/devtools/BUILD.gn
[rename] https://crrev.com/cf853f861018bf40bb283f50f12cade69db0091e/third_party/WebKit/Source/devtools/front_end/dom_extension/DOMExtension.js
[add] https://crrev.com/cf853f861018bf40bb283f50f12cade69db0091e/third_party/WebKit/Source/devtools/front_end/dom_extension/module.json
[modify] https://crrev.com/cf853f861018bf40bb283f50f12cade69db0091e/third_party/WebKit/Source/devtools/front_end/inspector.json
[modify] https://crrev.com/cf853f861018bf40bb283f50f12cade69db0091e/third_party/WebKit/Source/devtools/front_end/toolbox.json
[modify] https://crrev.com/cf853f861018bf40bb283f50f12cade69db0091e/third_party/WebKit/Source/devtools/front_end/toolbox_bootstrap/module.json
[modify] https://crrev.com/cf853f861018bf40bb283f50f12cade69db0091e/third_party/WebKit/Source/devtools/front_end/ui/module.json
[modify] https://crrev.com/cf853f861018bf40bb283f50f12cade69db0091e/third_party/WebKit/Source/devtools/front_end/unit_test_runner.json