Bugzilla

My rough understanding is that this operates on a per-block-formatting-context basis -- so to share a max-num-lines between title + blurb, you need to put them in the same BFC, inside of the same explicit flex item. Like this:
  https://jsfiddle.net/L54qgcsf/1/

I'm using a larger font-size on the title, like we do on the new-tab page.  Also, I've only tested this in Chrome so far, but hopefully it'll work in the next Firefox nightly. If not, it's a bug. :)

(Also: with the larger font-size, I'm not sure a fixed number of lines for the whole thing is really what you want... note that 6 lines of title-text will be a good bit taller than 6 lines of body text.)

My rough understanding is that this operates on a per-block-container basis -- so to share a max-num-lines between title + blurb, you need to put them in the same block (same non-anonymous flex item), and neither the title nor the blurb can itself be a block, I think... Like this:
  https://jsfiddle.net/L54qgcsf/1/

I'm using a larger font-size on the title, like we do on the new-tab page.  Also, I've only tested this in Chrome so far, but hopefully it'll work in the next Firefox nightly. If not, it's a bug. :)

(Also: with the larger font-size, I'm not sure a fixed number of lines for the whole thing is really what you want... note that 6 lines of title-text will be a good bit taller than 6 lines of body text.)