Fixes #8310. Make sure that sibling selectors (+,~) in some edge case…

…s don't leave modification behind in the DOM.

Follow up to 8b34687 which caused Sizzle to sometimes
leave modifications behind in the DOM and remove the id attribute on the wrong element.

sizzle.js

@@ -1157,7 +1157,8 @@ if ( document.querySelectorAll ) {
 				// and working up from there (Thanks to Andrew Dupont for the technique)
 				// IE 8 doesn't work on object elements
 				} else if ( context.nodeType === 1 && context.nodeName.toLowerCase() !== "object" ) {
-					var old = context.getAttribute( "id" ),
+					var oldContext = context,
+						old = context.getAttribute( "id" ),
 						nid = old || id,
 						hasParent = context.parentNode,
 						relativeHierarchySelector = /^\s*[+~]/.test( query );
@@ -1179,7 +1180,7 @@ if ( document.querySelectorAll ) {
 					} catch(pseudoError) {
 					} finally {
 						if ( !old ) {
-							context.removeAttribute( "id" );
+							oldContext.removeAttribute( "id" );
 						}
 					}
 				}

test/unit/selector.js

@@ -228,7 +228,7 @@ test("multiple", function() {
 });
 
 test("child and adjacent", function() {
-	expect(29);
+	expect(33);
 	t( "Child", "p > a", ["simon1","google","groups","mark","yahoo","simon"] );
 	t( "Child", "p> a", ["simon1","google","groups","mark","yahoo","simon"] );
 	t( "Child", "p >a", ["simon1","google","groups","mark","yahoo","simon"] );
@@ -253,6 +253,11 @@ test("child and adjacent", function() {
 	same( jQuery("#siblingfirst").find("~ em").get(), q("siblingnext"), "Element Preceded By with a context." );
 	same( jQuery("#siblingfirst").find("+ em").get(), q("siblingnext"), "Element Directly Preceded By with a context." );
 
+	equal( jQuery("#listWithTabIndex").length, 1, "Parent div for next test is found via ID (#8310)" );
+	equal( jQuery("#listWithTabIndex li:eq(2) ~ li").length, 1, "Find by general sibling combinator (#8310)" );
+	equal( jQuery("#__sizzle__").length, 0, "Make sure the temporary id assigned by sizzle is cleared out (#8310)" );
+	equal( jQuery("#listWithTabIndex").length, 1, "Parent div for previous test is still found via ID (#8310)" );
+
 	t( "Verify deep class selector", "div.blah > p > a", [] );
 
 	t( "No element deep selector", "div.foo > span > a", [] );