Update dartdoc to 0.27.0.

Release notes:  https://github.com/dart-lang/dartdoc/releases/tag/v0.27.0

Change-Id: I7cdd2437d1e8d4178462e9cd4fe49fa61d45c3d9
Reviewed-on: https://dart-review.googlesource.com/c/88380
Commit-Queue: Janice Collins <jcollins@google.com>
Reviewed-by: Devon Carew <devoncarew@google.com>
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 4c6ea38..3203185 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -84,6 +84,10 @@
 
         * `--new-deferred-split`: enables the new algorithm.
 
+#### dartdoc
+
+* dartdoc default styles now work much better on mobile.  Simple browsing
+  and searching of API docs now work in many cases.
 
 #### Pub
 
diff --git a/DEPS b/DEPS
index e88a9ea..beab68c 100644
--- a/DEPS
+++ b/DEPS
@@ -81,7 +81,7 @@
   # For more details, see https://github.com/dart-lang/sdk/issues/30164
   "dart_style_tag": "1.2.2",  # Please see the note above before updating.
 
-  "dartdoc_tag" : "v0.26.1",
+  "dartdoc_tag" : "v0.27.0",
   "file_rev": "515ed1dd48740ab14b625de1be464cb2bca4fefd",  # 5.0.6
   "fixnum_tag": "0.10.9",
   "func_rev": "25eec48146a58967d75330075ab376b3838b18a8",