[llvm] [ADT] Move shrink_and_clear to DenseMapBase (NFC) (PR #165103)

[Kazu Hirata via llvm-commits]

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@@ -1168,6 +1146,20 @@ class SmallDenseMap
     deallocate_buffer(OldRep.Buckets, sizeof(BucketT) * OldRep.NumBuckets,
                       alignof(BucketT));
   }
+
+  std::pair<bool, unsigned> planShrinkAndClear() const {
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kazutakahirata wrote:

Done.

https://github.com/llvm/llvm-project/pull/165103