I set my CSS like this:
.container {
display: grid;
grid-template-rows: auto 1fr 7%;
}
I went over to https://autoprefixer.github.io/ which transformed it to:
.container {
width: 100%;
display: -ms-grid;
display: grid;
-ms-grid-rows: auto 1fr 7%;
grid-template-rows: auto 1fr 7%;
}
The originally basically ignored 1fr such that the second row is its natural height. The ms-specific code made the first row just disappear, the second row lose its 100% width, and then nothing else. Edge, chrome, etc is not impacted at all by the change as expected. Not sure the proper way to get 100% fill here.