We now store two independent locations for an omni.jar, allowing GRE/XRE and
XUL application to each have their own omni.jar. And since xulrunner setups
are very independent from the XUL applications, we implement support for both
omni.jar and non omni.jar cases in the same runtime, with the side effect of
allowing to switch from one to the other manually without rebuilding the
binaries.
We let the mozilla::Omnijar API handle both cases, so that callers don't need
too much work to support them.
We also make the preferences service load the same set of preferences in all
the various cases (unified vs. separate, omni.jar vs. no omni.jar).
The child process launcher for IPC is modified to pass the base directories
needed for the mozilla::Omnijar API initialization in the child process.
Finally, the startupcache file name canonicalization is modified to separate
APP and GRE resources.
