Add Preview to templates-sdk develop nav and global nav in templates-sdk-dev. Remove dependence on -includePreview.

Change-Id: I1456c3c94522f58c7d1c899ff96dd95cdc6ada7c
diff --git a/tools/droiddoc/templates-sdk-dev/customizations.cs b/tools/droiddoc/templates-sdk-dev/customizations.cs
index d36e79f..15e8490 100644
--- a/tools/droiddoc/templates-sdk-dev/customizations.cs
+++ b/tools/droiddoc/templates-sdk-dev/customizations.cs
@@ -196,6 +196,8 @@
         <?cs include:"../../../../frameworks/base/docs/html/google/google_toc.cs" ?>
       <?cs elif:samples ?>
         <?cs include:"../../../../frameworks/base/docs/html/samples/samples_toc.cs" ?>
+      <?cs elif:preview ?>
+        <?cs include:"../../../../frameworks/base/docs/html/preview/preview_toc.cs" ?>
       <?cs elif:distribute ?>
         <?cs if:googleplay ?>
           <?cs include:"../../../../frameworks/base/docs/html/distribute/googleplay/googleplay_toc.cs" ?>