This patch adds a FooPrototype and FooConstructor class for each IDL
interface we generate JS bindings for.
These classes are very primitive and don't do everything they should
yet, but we have to start somewhere. :^)
Work towards #4789
The generic is<T>() uses dynamic_cast which is fine in the majority
of cases, but when one of them shows up in profiles, we can make it
faster by answering the is-a question manually.
To support this, the GUI process and the WebContent service will now
coordinate their backing store bitmaps. Each backing store can be
referred to by a serial ID, and we don't need to keep resending it
as a file descriptor.
We should probably do something similar in WindowServer. :^)
