Bug 884245 - Simplify nsContentUtils::GetDocumentFromCaller. r=bz

The first three lines of this function are an obvious bug. But the behavior in
general is also worrisome, because it's using antiquated XPConnect machinery
that will be less and less correct as we move to the new DOM bindings. Let's
just infer our global from the active compartment.
Bug 884362 - Use AutoJSContext in nsScriptSecurityManager::LoadPolicy. r=bz

This cx is just used for rooting etc. As such, we really just want whatever
cx is on the stack, but want a default if the stack-top cx is null (which it
sometimes is, here). And that's exactly what AutoJSContext gives us.
Bug 884362 - Make IDBRequest::CaptureCaller use the cx stack and decxify a bunch of IDB. r=bent
Bug 884362 - Play Maybe<> games to root |temp| in the right circumstances. r=bz
Bug 883450 - MOZ_CRASH if we fail to spin up the SafeJSContext, and remove error handling. r=gabor

There's not a lot we can do without it in the browser these days.
Bug 883450 - Unscope the JSAutoRequest in XPCJSContextStack. r=gabor
Bug 883450 - Remove custom request munging in XPCCallContext and use a JSAutoRequest. r=gabor
Bug 883450 - Re-order stuff in CallSetup so that we construct the RootedObject after the Push. r=bz
Bug 883450 - Miscellaneous requests. r=gabor
Bug 883450 - Assert that we're in a request whenever we create a Rooted<T>. r=terrence
Bug 885014 - Remove unused variable 'rv' in nsWebBrowser::EnableGlobalHistory. r=tbsaunde
Bug 885024 - "ASSERTION: FindAncestorForm should not be called if @form is set!". r=bz