Apply an accessible name to form.

The spec says that the "form" role only makes it a "landmark" if there
is an accessible name.

ARIA 1.3 says that the form role is a sub-role of landmark:
https://w3c.github.io/aria/, so if there is no accessible role then
the "form" role is inappropriate.

Since HTML-AAM doesn't say what the role should be otherwise (maybe
it should be "section"? That's what Chromium currently does), I
did not add a testcase for that situation.

Bug: 41490744

Change-Id: I6c6a93485a55a6645547cdf9e4eb4c8751e45141
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5384597
Commit-Queue: Chris Harrelson <chrishtr@chromium.org>
Reviewed-by: Aaron Leventhal <aleventhal@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1276910}
diff --git a/html-aam/roles.html b/html-aam/roles.html
index 7cfb285..387acc2 100644
--- a/html-aam/roles.html
+++ b/html-aam/roles.html
@@ -66,7 +66,7 @@
 <!-- todo: figcaption -->
 <figure data-testname="el-figure" data-expectedrole="figure" class="ex"><img alt="x" src="data:image/gif;base64,R0lGODlhAQABAIAAAP///wAAACH5BAEAAAAALAAAAAABAAEAAAICRAEAOw=="><figcaption>x</figcaption></figure>
 <!-- footer -> ./roles-contextual.html -->
-<form data-testname="el-form" data-expectedrole="form" class="ex"><input></form>
+<form aria-label="form" data-testname="el-form" data-expectedrole="form" class="ex"><input></form>
 <!-- todo: form-associated custom element -->
 
 <!-- el-h1-h6 -->
@@ -203,4 +203,4 @@
 </script>
 
 </body>
-</html>
\ No newline at end of file
+</html>