I was tasked with investigating why on large pages, mobile takes
longer to load a page then VE.
To do this I loaded a template heavy page in both mobile and desktop
and ran JavaScript profiling on both.


In desktop7.9% of  time was spent in jQuery.extend.css - this was the
most heavy function. In mobile it was also the most heavy - however in
mobile a whopping 23.76% of time was spent in jQuery.extend.css

In mobile 14360 calls were made to by both desktop and mobile to get
the value of float.

Looking closer at what was calling these I found it was related to
phantom element.

So it looks like fixing the following bug:
https://bugzilla.wikimedia.org/show_bug.cgi?id=64709
will help improve performance in mobile drastically.

I imagine the slowdown is related to the fact that on desktop existing
content is replaced with VisualEditor interface but on mobile there
are more DOM elements as VisualEditor is opened in an overlay on top
of the content.

Specifically the calls inside this callback that hog the most are:
1) $this.css( 'float' );
2) node.$.context.importNode( $shieldTemplate[0], true )

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