Add a comment describing the conversion from SourceRange to CharSourceRange.
Add a comment describing the conversion from SourceRange to CharSourceRange.

This is related to Xi's recent change, though it's been this way for
quite a while. Good thing this is just a debugging interface.

Swift SVN r32026

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