Import Cobalt 19.master.0.203780 Includes the following patches: https://cobalt-review.googlesource.com/c/cobalt/+/5210 by errong.leng@samsung.com https://cobalt-review.googlesource.com/c/cobalt/+/5270 by linus.wang@samsung.com

diff --git a/src/third_party/web_platform_tests/selection/getRangeAt.html b/src/third_party/web_platform_tests/selection/getRangeAt.html
new file mode 100644
index 0000000..3c6d797
--- /dev/null
+++ b/src/third_party/web_platform_tests/selection/getRangeAt.html

@@ -0,0 +1,14 @@
+<!DOCTYPE html>
+<title>The getRangeAt method</title>
+<div id=log></div>
+<script src=/resources/testharness.js></script>
+<script src=/resources/testharnessreport.js></script>
+<script>
+test(function() {
+  var sel = getSelection();
+  var range = document.createRange();
+  sel.addRange(range);
+  assert_throws("INDEX_SIZE_ERR", function() { sel.getRangeAt(-1); })
+  assert_throws("INDEX_SIZE_ERR", function() { sel.getRangeAt(1); })
+});
+</script>