Change record status: 
Project: 
Introduced in branch: 
8.2.x
Description: 

Summary

This change keeps HTML5shiv for backwards compatibility in the Stable and Classy themes which are API. @see
https://www.drupal.org/theme-guide/8/defining-a-theme
base theme:

Recommended. The theme can inherit the resources from another theme by defining it as a base theme. It is recommended to inherit from classy or stable, to ensure your own theme is more stable to any potential future changes in core theming.

Since we don't support IE8 and below we've removed this from Core, Seven and Bartik themes.

@see https://www.drupal.org/node/1569578 for the decision to not support IE8 and below.

Impacts: 
Site builders, administrators, editors
Themers
Updates Done (doc team, etc.)
Online documentation: 
Not done
Theming guide: 
Not done
Module developer documentation: 
Not done
Examples project: 
Not done
Coder Review: 
Not done
Coder Upgrade: 
Not done
Other: 
Other updates done