Add class="external" to the small_source_link.

+ actually fix api-gen test (that's howe the golden api_cache file got out of sync).

PiperOrigin-RevId: 444814024

Author: MarkDaoust

tools/tensorflow_docs/api_generator/pretty_docs/base_page.py

@@ -486,15 +486,14 @@ def top_source_link(location):
   return table
 
 
-def small_source_link(location):
+def small_source_link(location, text='View source'):
   """Returns a small source link."""
-  template = '<a target="_blank" href="{url}">View source</a>\n\n'
-
-  if not location.url:
+  if location.url:
+    return ('<a target="_blank" class="external" '
+            f'href="{location.url}">{text}</a>\n\n')
+  else:
     return ''
 
-  return template.format(url=location.url)
-
 
 def build_collapsable_aliases(aliases: List[str]) -> str:
   """Returns the top "Aliases" line."""

tools/tensorflow_docs/api_generator/pretty_docs/pretty_docs_test.py

@@ -54,7 +54,7 @@ def test_other_source_link_after_table(self):
 
        </table>
 
-       <a target="_blank" href="{url}">View source</a>
+       <a target="_blank" class="external" href="{url}">View source</a>
 
        """)
     self.assertEqual(expected, table)