Revert of Convert first letter into a pseudo element. (patchset #49 id:1570001 of https://codereview.chromium.org/571603003/)

Reason for revert:
Causing clusterfuzz regressions.

Original issue's description:
> Convert first letter into a pseudo element.
> 
> Currently, first letter renderers are created and destroyed through the updateFirstLetters() call in
> RenderBlock. This has, historically, been problematic as we may miss places where the call
> was required, leading to accessing invalid memory.
> 
> This CL converts the first letter code to use a PseudoElement for the first-letter instead of
> creating classes during layout.
> 
> With the PseudoElement implementation the two tests which are currently in
> LayoutTests/fast/css/first-letter-removed-added.html work as expected.
> 
> BUG=391288
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=183913

TBR=jchaffraix@chromium.org,eseidel@chromium.org,esprehn@chromium.org,leviw@chromium.org,pdr@chromium.org
BUG=391288

Review URL: https://codereview.chromium.org/639863006

git-svn-id: svn://svn.chromium.org/blink/trunk@184113 bbb929c8-8fbe-4397-9dbb-9b2b20218538