Fix overlapping timeline indicator

The selected data point indicator on timeline was often hidden behind
other data points. This CL changes its behaviour to ensure it is always
visible.

Test: yarn run dev
Bug:
Change-Id: Ide13e97ac7ab54e20cc6213be2ccdadce3d567a7
Merged-In: Ide13e97ac7ab54e20cc6213be2ccdadce3d567a7
1 file changed