url_formatter: Update comments for clarity.

components/url_formatter/url_formatter_unittest.cc

Index: components/url_formatter/url_formatter_unittest.cc
diff --git a/components/url_formatter/url_formatter_unittest.cc b/components/url_formatter/url_formatter_unittest.cc
index c0fe9509a6d4ac21a85ed744678e9468412c3155..128c4c3f80d13b4f206bb62a10dcd8a9f72cb15d 100644
--- a/components/url_formatter/url_formatter_unittest.cc
+++ b/components/url_formatter/url_formatter_unittest.cc
@@ -27,11 +27,28 @@ using base::ASCIIToUTF16;
 const size_t kNpos = base::string16::npos;
 
 struct IDNTestCase {
+  // The IDNA/Punycode version of the domain (plain ASCII).
   const char* const input;
+  // The equivalent Unicode version of the domain. Even if we expect the domain
+  // to be displayed in Punycode, this should still contain the Unicode
+  // equivalent (see |unicode_allowed|).
   const wchar_t* unicode_output;
+  // Whether we expect the domain to be displayed decoded as a Unicode string
+  // (true) or in its Punycode form (false).
   const bool unicode_allowed;
 };
 
+// These cases can be generated with the following simple Python function:
+// import codecs
+// def make_case(case_name, unicode_domain, unicode_allowed=True):
+//   idna_input = codecs.encode(unicode_domain, 'idna').decode('ascii')
+//   unicode_output = 'L' + (ascii(unicode_domain)
+//                           .replace("'", '"')
+//                           .replace('\\u', '\\x'))
+//   print('  // %s' % case_name)
+//   print('  {"%s", %s, %s},' %
+//         (idna_input, unicode_output, repr(unicode_allowed).lower()))

[Peter Kasting, 2017/02/06 21:54:14]

You said this didn't warrant a separate tool, but it honestly seems like the
better route would be to just go ahead and check this script in in a tools
directory, then have the comment note that it can be used?  I dunno.

+
 const IDNTestCase idn_cases[] = {
   // No IDN
   {"www.google.com", L"www.google.com", true},