preloaded-classes: Add android.text.Html$HtmlParser

This class creates a singleton HTMLSchema instance in <clinit> and
we want this done in the zygote. HTMLSchema.<init> is too large for
the compiler and can allocate ~100k of objects on the heap. This also
saves ~50ms in the execution of Html.fromHtml on a lightly loaded
marlin-userdebug.

Test: manual
Bug: 36678451
Change-Id: Icdd3af35018bbe283b3e3690c696e6517452165d