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.
We currently compile the Qt event loop files multiple times, for every
target which wants to use them. This patch moves these to LibWebView as
a central location to avoid this.
