Migrate some tests to the new htmlRunner

Fix events.get_timeStamp (was events.get_timestamp, wrong casing).

Rename `newRunner` to `htmlRunner`.

move tests to src/tests (from src/browser/tests). src/runtime and possibly other
parts might want to have html tests too.

src/tests/css.html

@@ -0,0 +1,5 @@
+<script src="testing.js"></script>
+<script id=support>
+  testing.expectEqual(true, CSS.supports('display: flex'));
+  testing.expectEqual(true, CSS.supports('text-decoration-style', 'blink'));
+</script>