Index: node_modules/autoprefixer/lib/hacks/user-select.js
===================================================================
--- node_modules/autoprefixer/lib/hacks/user-select.js	(revision 2058e5c694bb6097866a5fe6503c519e8f74970f)
+++ node_modules/autoprefixer/lib/hacks/user-select.js	(revision 2058e5c694bb6097866a5fe6503c519e8f74970f)
@@ -0,0 +1,33 @@
+let Declaration = require('../declaration')
+
+class UserSelect extends Declaration {
+  /**
+   * Avoid prefixing all in IE
+   */
+  insert(decl, prefix, prefixes) {
+    if (decl.value === 'all' && prefix === '-ms-') {
+      return undefined
+    } else if (
+      decl.value === 'contain' &&
+      (prefix === '-moz-' || prefix === '-webkit-')
+    ) {
+      return undefined
+    } else {
+      return super.insert(decl, prefix, prefixes)
+    }
+  }
+
+  /**
+   * Change prefixed value for IE
+   */
+  set(decl, prefix) {
+    if (prefix === '-ms-' && decl.value === 'contain') {
+      decl.value = 'element'
+    }
+    return super.set(decl, prefix)
+  }
+}
+
+UserSelect.names = ['user-select']
+
+module.exports = UserSelect