perf: fix infuriating mouseover flicker in dashboard graphs
perf: fix infuriating mouseover flicker in dashboard graphs

Change-Id: I9f5a6321a9481c4286a9e9a28bb8839f785d6d34
Reviewed-on: https://go-review.googlesource.com/c/build/+/412381
Reviewed-by: Michael Pratt <e7f1edc6d5aa9f6c8c377425db8f1a5816cbbb88@google.com>

golang/build,golang/build,golang/build,golang/build