Add some serialization debug guards.
Add some serialization debug guards.

No functionality change.

Swift SVN r5746

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tin/swift,khizkhiz/swift,sschiau/swift,Jnosh/swift,harlanhaskins/swift,shahmishal/swift,amraboelela/swift,jopamer/swift,stephentyrone/swift,MukeshKumarS/Swift,uasys/swift,jtbandes/swift,airspeedswift/swift,jtbandes/swift,dduan/swift,tjw/swift,zisko/swift,hughbe/swift,milseman/swift,shajrawi/swift,lorentey/swift,arvedviehweger/swift,swiftix/swift.old,sdulal/swift,kperryua/swift,shahmishal/swift,kperryua/swift,ken0nek/swift,JGiola/swift,jtbandes/swift,hughbe/swift,jopamer/swift,russbishop/swift,calebd/swift,stephentyrone/swift,aschwaighofer/swift,hooman/swift,modocache/swift,felix91gr/swift,austinzheng/swift,IngmarStein/swift,swiftix/swift.old,LeoShimonaka/swift,milseman/swift,jopamer/swift,therealbnut/swift,allevato/swift,jopamer/swift,airspeedswift/swift,therealbnut/swift,deyton/swift,swiftix/swift.old,swiftix/swift,ahoppen/swift,brentdax/swift,kusl/swift,tkremenek/swift,emilstahl/swift,deyton/swift,tardieu/swift,OscarSwanros/swift,karwa/swift,roambotics/swift,kusl/swift,karwa/swift,therealbnut/swift,zisko/swift,brentdax/swift,xedin/swift,natecook1000/swift,dduan/swift,practicalswift/swift,jtbandes/swift,modocache/swift,allevato/swift,gmilos/swift,xedin/swift,devincoughlin/swift,tjw/swift,karwa/swift,jopamer/swift,airspeedswift/swift,bitjammer/swift,sschiau/swift,xedin/swift,frootloops/swift,modocache/swift,shahmishal/swift,swiftix/swift.old,IngmarStein/swift,KrishMunot/swift,apple/swift,huonw/swift,gribozavr/swift,harlanhaskins/swift,MukeshKumarS/Swift,bitjammer/swift,djwbrown/swift,mightydeveloper/swift,huonw/swift,airspeedswift/swift,CodaFi/swift,milseman/swift,kusl/swift,kentya6/swift,mightydeveloper/swift,danielmartin/swift,LeoShimonaka/swift,jmgc/swift,allevato/swift,tinysun212/swift-windows,LeoShimonaka/swift,CodaFi/swift,bitjammer/swift,cbrentharris/swift,austinzheng/swift,kusl/swift,nathawes/swift,benlangmuir/swift,JaSpa/swift,Ivacker/swift,manavgabhawala/swift,kentya6/swift,kentya6/swift,zisko/swift,Ivacker/swift,johnno1962d/swift,Jnosh/swift,tjw/swift,frootloops/swift,shahmishal/swift,atrick/swift,devincoughlin/swift,codestergit/swift,xedin/swift,amraboelela/swift,khizkhiz/swift,Ivacker/swift,nathawes/swift,kentya6/swift,natecook1000/swift,jtbandes/swift,arvedviehweger/swift,glessard/swift,kusl/swift,kstaring/swift,parkera/swift,harlanhaskins/swift,deyton/swift,karwa/swift,SwiftAndroid/swift,emilstahl/swift,swiftix/swift.old,manavgabhawala/swift,austinzheng/swift,slavapestov/swift,milseman/swift,codestergit/swift,practicalswift/swift,xwu/swift,return/swift,uasys/swift,nathawes/swift,airspeedswift/swift,Ivacker/swift,rudkx/swift,felix91gr/swift,ahoppen/swift,austinzheng/swift,hughbe/swift,SwiftAndroid/swift,johnno1962d/swift,harlanhaskins/swift,harlanhaskins/swift,MukeshKumarS/Swift,uasys/swift,roambotics/swift,ben-ng/swift,hughbe/swift,Jnosh/swift,johnno1962d/swift,calebd/swift,benlangmuir/swift,hughbe/swift,devincoughlin/swift,ben-ng/swift,practicalswift/swift,ben-ng/swift,return/swift,aschwaighofer/swift,djwbrown/swift,natecook1000/swift,glessard/swift,johnno1962d/swift,austinzheng/swift,roambotics/swift,adrfer/swift,sschiau/swift,dduan/swift,OscarSwanros/swift,calebd/swift,cbrentharris/swift,natecook1000/swift,therealbnut/swift,slavapestov/swift,amraboelela/swift,MukeshKumarS/Swift,adrfer/swift,bitjammer/swift,apple/swift,sdulal/swift,djwbrown/swift,MukeshKumarS/Swift,kstaring/swift,zisko/swift,tkremenek/swift,allevato/swift,gottesmm/swift,tardieu/swift,uasys/swift,jckarter/swift,Ivacker/swift,lorentey/swift,JaSpa/swift,CodaFi/swift,tkremenek/swift,xwu/swift,natecook1000/swift,tjw/swift,frootloops/swift,cbrentharris/swift,ken0nek/swift,SwiftAndroid/swift,arvedviehweger/swift,gmilos/swift,huonw/swift,milseman/swift,manavgabhawala/swift,slavapestov/swift,dreamsxin/swift,huonw/swift,devincoughlin/swift,kentya6/swift,kstaring/swift,calebd/swift,allevato/swift,swiftix/swift,JaSpa/swift,glessard/swift,brentdax/swift,gregomni/swift,felix91gr/swift,lorentey/swift,Jnosh/swift,jckarter/swift,tinysun212/swift-windows,sschiau/swift,shajrawi/swift,nathawes/swift,Ivacker/swift,return/swift,dreamsxin/swift,natecook1000/swift,danielmartin/swift,khizkhiz/swift,xwu/swift,milseman/swift,brentdax/swift,atrick/swift,parkera/swift,sdulal/swift,shahmishal/swift,KrishMunot/swift,emilstahl/swift,tjw/swift,parkera/swift,emilstahl/swift,JaSpa/swift,ben-ng/swift,deyton/swift,glessard/swift,jtbandes/swift,kperryua/swift,stephentyrone/swift,emilstahl/swift,natecook1000/swift,tinysun212/swift-windows,roambotics/swift,JaSpa/swift,johnno1962d/swift,return/swift,atrick/swift,tardieu/swift,tkremenek/swift,aschwaighofer/swift,kstaring/swift,karwa/swift,IngmarStein/swift,tjw/swift,gmilos/swift,sschiau/swift,jmgc/swift,ben-ng/swift,kstaring/swift,roambotics/swift,kentya6/swift,atrick/swift,jmgc/swift,gottesmm/swift