(...and ASSERT_NOT_REACHED => VERIFY_NOT_REACHED)
Since all of these checks are done in release builds as well,
let's rename them to VERIFY to prevent confusion, as everyone is
used to assertions being compiled out in release.
We can introduce a new ASSERT macro that is specifically for debug
checks, but I'm doing this wholesale conversion first since we've
accumulated thousands of these already, and it's not immediately
obvious which ones are suitable for ASSERT.
Now that WindowServer broadcasts the system theme using an anonymous
file, we need clients to pledge "recvfd" so they can receive it.
Some programs keep the "shared_buffer" pledge since it's still used for
a handful of things.
Whilst SystemMenu maintains a constant WindowServer connection, there
isn't always a Window active on that connection to listen for theme
changes - this causes the current theme in this process to fall out of
sync with the rest of the system. This fixes this problem by
re-requesting an UpdateSystemTheme message when the dialog is
instantiated.