Add utility method to DenseMap to return the amount of memory used for its buckets.
Add utility method to DenseMap to return the amount of memory used for its buckets.

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@130382 91177308-0d34-0410-b5e6-96231b3b80d8

apple/swift-llvm,chubbymaggie/asap,apple/swift-llvm,chubbymaggie/asap,chubbymaggie/asap,GPUOpen-Drivers/llvm,chubbymaggie/asap,llvm-mirror/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,dslab-epfl/asap,dslab-epfl/asap,llvm-mirror/llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,llvm-mirror/llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,chubbymaggie/asap,chubbymaggie/asap,dslab-epfl/asap,dslab-epfl/asap,llvm-mirror/llvm,apple/swift-llvm,apple/swift-llvm,apple/swift-llvm,dslab-epfl/asap,apple/swift-llvm,dslab-epfl/asap,GPUOpen-Drivers/llvm,dslab-epfl/asap,llvm-mirror/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm