After change log rendering method, to append HTML elements instead of
rerendering the entire thing, the case of gradual rendering of a log
started to behave much better (because we just append new elements), but
the initial render took a bit longer, because of the fact that appending
large separate HTML elements to DOM at once is not a good idea.
In order to make the situation better I added simple optimization.
Elements are added to DocumentFragment node before inserting to DOM and
appended to DOM only after all elements are processed. That way, when
log needs to be rendered all at once, we will not do any DOM operations
until log is ready.
