Reproducible in 52.0.2743.82 Stable.

Bumping this to M54 because it's not a recent regression, and I won't be able to get a good fix in time for M53

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/18477b7e830c6726c2987e406ce7dd014b418975

commit 18477b7e830c6726c2987e406ce7dd014b418975
Author: spqchan <spqchan@chromium.org>
Date: Fri Aug 12 22:27:16 2016

[Mac] Fix for fullscreen toolbar dropdown

Remove a line that was setting the toolbar fraction to 0, when the
fullscreen toolbar is toggled between show and hidden. This was
causing the toolbar to have incorrect toolbar fraction values.

BUG= 634981 

Review-Url: https://codereview.chromium.org/2240293003
Cr-Commit-Position: refs/heads/master@{#411799}

[modify] https://crrev.com/18477b7e830c6726c2987e406ce7dd014b418975/chrome/browser/ui/cocoa/browser_window_controller.mm

Rechecked this on chrome version 54.0.2830.0 on MAC 10.11.6, followed the below steps:

Steps Followed:
===============
1) ⌘ + Ctrl + f - To make tab strip in fullscreen off.
2) Opened two 2 tabs in a window and entered fullscreen
3) Mousing into menu-bar will show menu-bar and tab strip
3) Using mouse, enabled showing tab strip in fullscreen
4) Moved mouse away and menu-bar hides
5) Using mouse again, disabled showing tab strip in full-screen and tab strip hides
6) Moved mouse away and menu-bar hides
7) Mouse back to the menubar, the tab strip is not shown (2 on 20 Instances I tried), only the menubar was displayed - Attached screenshot for the same.

@ pinkerton: Could you please let us know if the steps followed was correct or did I missed out anything here.

Deleted: Tab Strip.png 636 KB

	Tab Strip.png 636 KB View Download

This still reproducible? I'll reopen this. I'm working on  Issue 637976  and the solution I'm working on might fix fullscreen toolbar stickiness. It looks like some of the legacy code might be causing this issue

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/cccd612ee508dd2ee75f5d70e46b33bb17a7b88f

commit cccd612ee508dd2ee75f5d70e46b33bb17a7b88f
Author: spqchan <spqchan@chromium.org>
Date: Fri Aug 19 01:46:46 2016

[Mac] Reworked FullscreenToolbarController

Removed mouse tracking for the menubar since it's unreliable
for multiple monitors and SplitScreen. Instead, use the menubar
Carbon events to update the toolbar.

Removed the animation delays because they were mostly unused.
When they actually were used, they would cause bugs and janky
movements. Cleaned up dead code and comments

BUG= 634981 ,  637976 ,  637514 

Review-Url: https://codereview.chromium.org/2256993002
Cr-Commit-Position: refs/heads/master@{#413018}

[modify] https://crrev.com/cccd612ee508dd2ee75f5d70e46b33bb17a7b88f/chrome/browser/ui/cocoa/bookmarks/bookmark_bar_controller.mm
[modify] https://crrev.com/cccd612ee508dd2ee75f5d70e46b33bb17a7b88f/chrome/browser/ui/cocoa/bookmarks/bookmark_bubble_controller.mm
[modify] https://crrev.com/cccd612ee508dd2ee75f5d70e46b33bb17a7b88f/chrome/browser/ui/cocoa/bookmarks/bookmark_bubble_observer_cocoa.mm
[modify] https://crrev.com/cccd612ee508dd2ee75f5d70e46b33bb17a7b88f/chrome/browser/ui/cocoa/bookmarks/bookmark_button.mm
[modify] https://crrev.com/cccd612ee508dd2ee75f5d70e46b33bb17a7b88f/chrome/browser/ui/cocoa/bookmarks/bookmark_editor_base_controller.mm
[modify] https://crrev.com/cccd612ee508dd2ee75f5d70e46b33bb17a7b88f/chrome/browser/ui/cocoa/browser_window_controller.h
[modify] https://crrev.com/cccd612ee508dd2ee75f5d70e46b33bb17a7b88f/chrome/browser/ui/cocoa/browser_window_controller.mm
[modify] https://crrev.com/cccd612ee508dd2ee75f5d70e46b33bb17a7b88f/chrome/browser/ui/cocoa/browser_window_controller_private.h
[modify] https://crrev.com/cccd612ee508dd2ee75f5d70e46b33bb17a7b88f/chrome/browser/ui/cocoa/browser_window_controller_private.mm
[modify] https://crrev.com/cccd612ee508dd2ee75f5d70e46b33bb17a7b88f/chrome/browser/ui/cocoa/fullscreen_toolbar_controller.h
[modify] https://crrev.com/cccd612ee508dd2ee75f5d70e46b33bb17a7b88f/chrome/browser/ui/cocoa/fullscreen_toolbar_controller.mm
[modify] https://crrev.com/cccd612ee508dd2ee75f5d70e46b33bb17a7b88f/chrome/browser/ui/cocoa/global_error_bubble_controller.mm
[modify] https://crrev.com/cccd612ee508dd2ee75f5d70e46b33bb17a7b88f/chrome/browser/ui/cocoa/location_bar/autocomplete_text_field.mm
[modify] https://crrev.com/cccd612ee508dd2ee75f5d70e46b33bb17a7b88f/chrome/browser/ui/cocoa/location_bar/autocomplete_text_field_editor.mm
[modify] https://crrev.com/cccd612ee508dd2ee75f5d70e46b33bb17a7b88f/chrome/browser/ui/cocoa/profiles/avatar_base_controller.mm

Reworked the fullscreen toolbar and removed the mouse tracking it was relying on. 
It's now less janky and overall much more reliable

Tested the issue on Latest Chrome# 54.0.2837.0 on Mac OS X 10.11.6 and is working as intended. Hence adding TE-Verified Labels. Below are the observations

(i) When "Always show Toolbar in Full Screen" is unchecked -- Moving mouse away from the tab strip, both tabstrip(along with omnibox) and Menubar hides.

(ii) When "Always show Toolbar in Full Screen" is checked -- Moving mouse away from the tab strip, only Menubar hides.

Thank You.