Add reference to sampling doc in heapprofd design. am: bae8193de6 am: bd6f709844 am: 61097a92e8 am: 1eb8e67e96
Add reference to sampling doc in heapprofd design. am: bae8193de6 am: bd6f709844 am: 61097a92e8 am: 1eb8e67e96

Original change: https://android-review.googlesource.com/c/platform/external/perfetto/+/1717713

Change-Id: I61cce78576d70e3264984f4b83cb13c5a57ff2d7

google/perfetto,google/perfetto,google/perfetto,google/perfetto,google/perfetto,google/perfetto,google/perfetto,google/perfetto