Build: Fix missing coverage from main browser tests

Move "sandboxed-iframe.html" test to the end.

Closes #1503.

Gruntfile.js

@@ -110,7 +110,6 @@ module.exports = function( grunt ) {
 						require.resolve( "grunt-contrib-qunit/chrome/bridge" )
 					],
 					urls: [
-						"test/sandboxed-iframe.html",
 						"test/index.html",
 						"test/autostart.html",
 						"test/startError.html",
@@ -145,7 +144,11 @@ module.exports = function( grunt ) {
 						"test/string-filter.html",
 						"test/module-only.html",
 						"test/module-skip.html",
-						"test/module-todo.html"
+						"test/module-todo.html",
+
+						// ensure this is last - it has the potential to drool
+						// and omit subsequent tests during coverage runs
+						"test/sandboxed-iframe.html"
 					].map( file => `http://localhost:${connectPort}/${file}` )
 				}
 			}