Revert of Elements whose contents start with an astral Unicode symbol disappear when CSS `::first-letter` is …

Revert of Elements whose contents start with an astral Unicode symbol disappear when CSS `::first-letter` is … (patchset #9 id:160001 of https://codereview.chromium.org/1133853006/ )

Reason for revert:
ASan picking up a number of UAF failures due to this one,

 http://build.chromium.org/p/chromium.webkit/builders/WebKit%20Linux%20ASAN/builds/19782

Original issue's description:
> Elements whose contents start with an astral Unicode symbol disappear when CSS `::first-letter` is applied to them.
> 
> This CL is inspired by http://trac.webkit.org/changeset/172513
> written by Myles C. Maxfield.
> The previous code assumed that all "characters" are exactly 1 16-bit code unit wide.
> Instead, use numCharactersInGraphemeClusters().
> 
> For blink, we add countCharactersAndGraphemesInCluster to bring a similar
> functionality to blink. This api is based on countGraphemesInCluster and improved
> to figure out the number of characters and grapheme at the same time in the given clusters.
> 
> BUG=401945
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=200227

TBR=leviw@chromium.org,eae@chromium.org,esprehn@chromium.org,drott@chromium.org,shivamidow@gmail.com
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=401945
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=200228

[sof, 2015-08-09 12:54:45]

Created Revert of Elements whose contents start with an astral Unicode symbol
disappear when CSS `::first-letter` is …