Correct $ref links in extensions documentation server relative location.

chrome/common/extensions/docs/server2/intro_data_source.py

Index: chrome/common/extensions/docs/server2/intro_data_source.py
diff --git a/chrome/common/extensions/docs/server2/intro_data_source.py b/chrome/common/extensions/docs/server2/intro_data_source.py
index c345a6e7a1604dab2a6e0b5c1be8db7d48b24564..883b3d360e1266d3e2e30425c1e8979c5eb9cde9 100644
--- a/chrome/common/extensions/docs/server2/intro_data_source.py
+++ b/chrome/common/extensions/docs/server2/intro_data_source.py
@@ -50,7 +50,7 @@ class IntroDataSource(DataSource):
     # Guess the name of the API from the path to the intro.
     api_name = os.path.splitext(intro_path.split('/')[-1])[0]
     intro_with_links = self._ref_resolver.ResolveAllLinks(
-            intro, namespace=api_name)
+            intro, relative_to=self._request.path, namespace=api_name)
 
     # The templates generate a title for intros based on the API name.
     expect_title = '/intros/' not in intro_path