Make html-escape also escape < and > in attributes.

tests/lib/convert/html_escape_test.dart

Index: tests/lib/convert/html_escape_test.dart
diff --git a/tests/lib/convert/html_escape_test.dart b/tests/lib/convert/html_escape_test.dart
index 8a13773d2fb3d77543d87f5c09ff457318ead329..a9d0b6717311672522a67558c21e47bb9004a2d3 100644
--- a/tests/lib/convert/html_escape_test.dart
+++ b/tests/lib/convert/html_escape_test.dart
@@ -14,10 +14,10 @@ const _OUTPUT_UNKNOWN = '<A </test> of \xA0 "double" '
   '& 'single' values>';
 
 const _OUTPUT_ATTRIBUTE =
-    "<A </test> of \xA0 &quot;double&quot; &amp; 'single' values>";
+    "&lt;A &lt;/test&gt; of \xA0 &quot;double&quot; &amp; 'single' values&gt;";
 
 const _OUTPUT_SQ_ATTRIBUTE =
-    '<A </test> of \xA0 "double" &amp; &#39;single&#39; values>';
+    '&lt;A &lt;/test&gt; of \xA0 "double" &amp; &#39;single&#39; values&gt;';
 
 const _OUTPUT_ELEMENT =
     """&lt;A &lt;/test&gt; of \xA0 "double" &amp; 'single' values&gt;""";