Luis Javier Merino authored Dec 29, 2021 and Tomaz Canabrava committed Jan 25, 2022

Using line lengths, moving up in scroll history would require traversing
line lengths adding them until getting the start of the required line.
Using line starts, removing lines as they scroll past history would
require traversing the whole vector and updating the line starts.  A
better option is storing biased line starts, which doesn't require any
traversing of the vector for common operations (hopefully reflowing is
not a common operation).