CSS Grid oveflow behaviour different in Firefox and Chrome

Question

I noticed different scrolling behaviour in Firefox and Chrome in the following snipped. In Firefox only the .main scrolls, in Chrome, the whole body scrolls. Am I doing something not to spec? Which browser is right? How can I get Chrome to behave like Firefox?

https://jsfiddle.net/Lgzb45np/

body {
  height: 100vh;
}

.container {
  display: grid;
  grid-template: 50px 1fr / 240px 1fr;
  height: 100%;
}

.header {
    grid-area: 1/1;
}
.sidebar {  
    grid-area: 2/1;
}
.main {  
  grid-area: 2/2;    
  height: 100%;
  overflow: auto;
}
.large-div{
  height: 800px;
}

<div class="container">
  <div class="header">Some Header Row</div>
  <div class="sidebar">A Sidebar</div>
  <div class="main">
  <div class="large-div">This is large</div>
  And Some More</div>
</div>

Answer 1

Removing the height: 100% from .main should work. You already define the height size of the .maincolumn (1fr)

CSS

.main {  
grid-area: 2/2;    
overflow: auto;
}

DEMO