perfetto-ui: Always show CPU slice
perfetto-ui: Always show CPU slice

CPU slices less than 1px width should always be drawn at 1px.

Change-Id: I20f1afc9314561e1d529445e53cbc67598503b0d
google/perfetto,google/perfetto,google/perfetto,google/perfetto,google/perfetto,google/perfetto,google/perfetto,google/perfetto