As usual, someone had the same idea and has provided a pre-coded solution. I discovered these resources in an attempt to help you with this very complicated task. You can use the code as written or place it into a bookmarklet.
I found a detailed article that describes how to use both the [Navigation Timing API][1] & the [Resource Timing API][2] The article I came across is titled (and found at):
[Assessing Loading Performance in Real Life with Navigation and Resource Timing][3]
The two prebuilt solutions provided by that article take completely different approaches to visualizing the data you seek.