[RewriteStatepointsForGC] Replace std::map with DenseMap
[RewriteStatepointsForGC] Replace std::map with DenseMap

I'd done the work of extracting the typedef in a previous commit, but didn't actually change it.  Hopefully this will make any subtle changes easier to isolate.



git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@230081 91177308-0d34-0410-b5e6-96231b3b80d8

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