css2: Add a test for 'float' on ':root'

Bug: 1323571
Change-Id: Ie0f60d58d67d14a48044d10f1b50db9c67e9e0a6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3932332
Auto-Submit: Kent Tamura <tkent@chromium.org>
Reviewed-by: Koji Ishii <kojii@chromium.org>
Commit-Queue: Koji Ishii <kojii@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1054044}
diff --git a/css/CSS2/floats/float-root-ref.html b/css/CSS2/floats/float-root-ref.html
new file mode 100644
index 0000000..1f593f4
--- /dev/null
+++ b/css/CSS2/floats/float-root-ref.html
@@ -0,0 +1,11 @@
+<!DOCTYPe html>
+<style>
+body {
+  float: right;
+  margin-top: 0;
+}
+</style>
+
+<body>
+<p>foo</p>
+</body>
diff --git a/css/CSS2/floats/float-root.html b/css/CSS2/floats/float-root.html
new file mode 100644
index 0000000..ee7f70e
--- /dev/null
+++ b/css/CSS2/floats/float-root.html
@@ -0,0 +1,13 @@
+<!DOCTYPe html>
+<link rel="help" href="https://w3c.github.io/csswg-drafts/css2/#propdef-float">
+<link rel="match" href="float-root-ref.html">
+
+<style>
+:root {
+  float: right;
+}
+</style>
+
+<body>
+<p>foo</p>
+</body>