When your health regenerate, whether it be natural regeneration from full hunger bar or from potions, the outlines of health bar does not flash once.
It used to happen prior to 1.7 but after 1.7, the health bar does not blink once when you regenerate.
Duplicate of MC-34815 - If you have not, please use the search function in the future, to see if your bug has already been submitted. If you could not find the original report, please comment with the keywords you searched for.