Bugzilla

Also: I can make older builds (before the regression range) reproduce the issue, with the original testcase, if I add
```
* { overflow: visible !important; }
```

So in old builds, we were being "saved" by some scrollable element improperly breaking a nested chain of `height:100%` elements. And bug 1595199 correctly fixed that by propagating a percent-height-resolution flag through scrollable elements, which means the scrollframe doesn't "save" us anymore.

So, the proximal regression here was from bug 1595199, which was a correctness fix that made us propagate a flag that we should have been propagating all along.  And the real lower-level issue here is long-time bug 792508.

Also: I can make older builds (before the regression range) reproduce the issue, with the original testcase, if I add
```
* { overflow: visible !important; }
```

So in old builds, we were being "saved" by some scrollable element effectively breaking a nested chain of `height:100%` elements. And bug 1595199 correctly fixed that by propagating a percent-height-resolution flag through scrollable elements, which means the scrollframe doesn't "save" us anymore.

So, the proximal regression here was from bug 1595199, which was a correctness fix that made us propagate a flag that we should have been propagating all along.  And the real lower-level issue here is long-time bug 792508.