DM: add --pipe

internal_links is failing across all three versions.  One of the rects doesn't draw.

BUG=
R=epoger@google.com

Author: mtklein@google.com

Review URL: https://codereview.chromium.org/47773002

git-svn-id: http://skia.googlecode.com/svn/trunk@11985 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/dm/README b/dm/README
index dbefe58..0c842cd 100644
--- a/dm/README
+++ b/dm/README
@@ -1,11 +1,12 @@
 DM is like GM, but multithreaded.  It doesn't do everything GM does yet.
 
 Current approximate list of missing features:
+  --config pdf
   --mismatchPath
   --missingExpectationsPath
   --writePicturePath
 
-  --deferred / --pipe
+  --deferred
   --rtree
   --tiledGrid