Fix the lldb WebCoreLayoutUnitProvider to not dynamically look up the LayoutUnit...

Fix the lldb WebCoreLayoutUnitProvider to not dynamically look up the LayoutUnit denominator
https://bugs.webkit.org/show_bug.cgi?id=153334

Reviewed by Zalan Bujtas.

Evaluating expressions in the LayoutUnit summary provider seems to cause
re-entrancy problems in lldb python bindings, so just hardcode the LayoutUnit
denominator to 64.

* lldb/lldb_webkit.py:
(WebCoreLayoutUnitProvider.to_string):

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@195444 268f45cc-cd09-0410-ab3c-d52691b4dbfc