Bug 1843968 - Hold some strong references. r=mccr8, a=dmeehan

docshell/base/BrowsingContext.cpp

docshell/base/CanonicalBrowsingContext.cpp

docshell/base/nsDocShell.cpp

docshell/base/nsDocShellTreeOwner.cpp

docshell/shistory/ChildSHistory.cpp

docshell/shistory/nsSHistory.cpp

dom/base/Location.cpp

dom/base/nsFrameLoader.cpp

dom/html/HTMLFormElement.cpp

dom/ipc/ContentChild.cpp

dom/ipc/ContentParent.cpp

dom/ipc/WindowGlobalParent.cpp

dom/l10n/DocumentL10n.cpp

dom/prototype/PrototypeDocumentContentSink.cpp

netwerk/ipc/DocumentLoadListener.cpp

parser/html/nsHtml5TreeOpExecutor.cpp

parser/prototype/PrototypeDocumentParser.cpp

toolkit/components/browser/nsWebBrowser.cpp

toolkit/components/sessionstore/SessionStoreUtils.cpp

xpfe/appshell/nsAppShellService.cpp