This is a uniform mechanism to access a number of bespoke boolean
flags in ParserOutput. It allows extensibility in core (by adding new
field names to ParserOutputFlags) without exposing new getter/setter
methods to Parsoid. It replaces the ParserOutput::{get,set}Flag()
interface which (a) doesn't allow access to certain flags, and (b) is
typically called with a string rather than a constant, and (c) has a
very generic name. (Note that Parser::setOutputFlag() already called
these "output flags".)
In the future we might unify the representation so that we store
everything in $mFlags and don't have explicit properties in
ParserOutput, but those representation details should be invisible to
the clients of this API. (We might also use a proper enumeration
for ParserOutputFlags, when PHP supports this.)
There is some overlap with ParserOutput::{get,set}ExtensionData(), but
I've left those methods as-is because (a) they allow for non-boolean
data, unlike the *Flag() methods, and (b) it seems worthwhile to
distingush properties set by extensions from properties used by core.
Code search:
https://codesearch.wmcloud.org/search/?q=%5BOo%5Dut%28put%29%3F%28%5C%28%5C%29%29%3F-%3E%28g%7Cs%29etFlag%5C%28&i=nope&files=&excludeFiles=&repos=
Bug: T292868
Change-Id: I39bc58d207836df6f328c54be9e3330719cebbeb
06ab90f163