In general, using an AutoJSAPI inited with an object is NOT the same as using
AutoSafeJSContext (or AutoJSAPI inited without an object) and then entering the
compartment of the object: the former will report exceptions to the global of
the object as it comes off the stack, while the latter will not. This only
really matters if we have an object from a window or worker global and hence
might fire error events, or report internal stuff to the web console.
The changes to initing with an object made in this bug are OK for the following
reasons:
1) dom/base/Console.cpp: Always clears its exception before coming off the stack.
2) dom/base/nsDOMClassInfo.cpp: Inits with a non-web global.
3) dom/base/nsFrameMessageManager.cpp: Inits with a non-web global.
4) dom/media/MediaPermissionGonk.cpp: We probably want the caller to notice if
anything here throws.
5) dom/xbl/nsXBLPrototypeBinding.cpp: Inits with a non-web global.
6) dom/xul/nsXULElement.cpp: Inits with a non-web global.
7) extensions/pref/autoconfig/src/nsJSConfigTriggers.cpp: Inits with a non-web global.
8) ipc/testshell/XPCShellEnvironment.cpp: Inits with a non-web global.
There are still a handful that either are used with other runtimes, or that
happen very early/late in cx the lifetime of various things where it doesn't
necessarily make sense to have a cx on the stack. This should definitely ensure
that we're not doing double-duty with the nsCxPusher change, though.
