Editor: Mobile: toolbar does not stay pinned to top

[designsimply]

Raised by @sandymcfadden

What I Did:
Tried scrolling the editor window in Chrome on Android

What I Expected:
Expected the toolbar to remain fixed at the top

What Actually Happened:
The toolbar disappeared to the top of the screen. When I scrolled back up it came back down into place.

https://cloudup.com/cnEc3k-4-un

Note from @rachelmcr

This also happens on iOS (8.4.1, iPhone 6) in Safari and Chrome. It's especially disruptive because as soon as you focus on the editor the cursor scrolls to the top of the screen, hiding the toolbar from view.

Note from @mtias

This is intended behaviour, pinning the toolbar in mobile didn't work well.

[ryanboren]

Has troubles staying pinned on Macnchrome too.

https://test.wordpress.com/2016/01/25/editor-toolbar-leaves-editor-when-scrolling-up-macnchrome/

[ryanboren]

I've developed the unfortunate habit of inducing elastic bounceback to "reset" the editor. Scrolling all the way up is necessary to unstick the toolbar. When the Visual and HTML tabs are on screen and the toolbar is not below it, I have trouble finding the toolbar. I scan around the content and title area until remembering, oh yeah, I have to scroll to top to reset. This hitch in editing flow is felt daily, repeatedly.

[aduth]

Mobile toolbar pinning was removed in 9569-gh-calypso-pre-oss with improvements in #1452. Remaining issues with desktop toolbar pinning are better covered by #337 and #4792, and are expected to be resolved by #4824.