Core: Drop support for Edge Legacy (i.e. non-Chromium Microsoft Edge)

Drop support for Edge Legacy: the non-Chromium, EdgeHTML-based Microsoft
Edge version. Also, restrict some workarounds that were applied
unconditionally in all browsers to run only in IE now. This slightly
increases the size but reduces the performance burden on modern browsers
that don't need the workarounds.

Also, clean up some comments & remove some obsolete workarounds.

Fixes gh-4568
Closes gh-4792

1 files changed, 6 insertions, 10 deletions

diff --git a/test/unit/selector.js b/test/unit/selector.js
index 1111e2460..b11b801c6 100644
--- a/test/unit/selector.js
+++ b/test/unit/selector.js
@@ -1661,14 +1661,10 @@ QUnit.test( "context", function( assert ) {
 	}
 } );
 
-// Support: IE 11+, Edge 12 - 18+
-// IE/Edge don't support the :scope pseudo-class so they will trigger MutationObservers.
+// Support: IE 11+
+// IE doesn't support the :scope pseudo-class so it will trigger MutationObservers.
 // The test is skipped there.
-QUnit[
-	( QUnit.isIE || /edge\//i.test( navigator.userAgent ) ) ?
-		"skip" :
-		"test"
-	]( "selectors maintaining context don't trigger mutation observers", function( assert ) {
+QUnit.testUnlessIE( "selectors maintaining context don't trigger mutation observers", function( assert ) {
 	assert.expect( 1 );
 
 	var timeout,
@@ -1742,10 +1738,10 @@ QUnit[ QUnit.jQuerySelectors ? "test" : "skip" ]( "disconnected nodes", function
 	assert.equal( $opt.is( ":selected" ), true, "selected option" );
 } );
 
-// Support: IE 11+, Edge 12 - 18+
-// IE/Edge don't support Shadow DOM.
+// Support: IE 11+
+// IE doesn't support Shadow DOM.
 // selector-native doesn't support querying inside of Shadow DOM.
-QUnit[ QUnit.jQuerySelectors && document.body.getRootNode ? "test" : "skip" ](
+QUnit[ QUnit.jQuerySelectors && !QUnit.isIE ? "test" : "skip" ](
 	"Shadow DOM nodes supported as root", function( assert ) {
 	assert.expect( 2 );