For Firefox DevTools, we will need to track WebViews by a numerical ID.
Here, we just increment a static 64-bit counter. We can switch to using
IDAllocator if we ever have an issue with this.
This patch adds such an ID to the views and a couple of APIs to access
WebViews after creation.
A couple of reasons:
- Origin's Host (when in the tuple state) can't be null
- There's an "empty host" concept in the spec which is NOT the same as a
null Host, and that was confusing me.
We will want to re-inform WebContent of the system visibility state when
we create a new process after a crash. This changes the IPC to just send
the enum value directly, instead of a boolean, so that we can just store
that enum value directly on the ViewImplementation class.
