Regression bug: points jump around when LASSOing with webGL

This was introduced some time between 2018-01-26 to 2018-03-07

df <- data.frame(x = runif(10000, min = 0, max = 20000), y = runif(10000, min = 0, max = 20000))
plot_ly(df, x = ~x, y= ~y) %>% add_markers() %>% toWebGL()

When the above code is run with plotly from 2018-01-26, selecting points works fine. But when run with a version from 2018-03-07, selecting points causes them to jump.

See video below

(originally reported in #1211)

首先使用 2018-01-26 和 2018-03-07 的 plotly.R 版本运行所提供的 R 复现，然后比较 WebGL 的选择行为，并检查这两个版本之间的回归问题。当在包含 10,000 个点的图中选择点不再导致点跳动时，即表示完成。