DM: run PDF except on Android bots.

While we work out RAM issues on Android, run everywhere else.

BUG=skia:

Review URL: https://codereview.chromium.org/971463004
diff --git a/tools/dm_flags.py b/tools/dm_flags.py
index a7ed8ca..f5a69de 100755
--- a/tools/dm_flags.py
+++ b/tools/dm_flags.py
@@ -31,6 +31,9 @@
       configs.extend(['msaa4', 'nvprmsaa4'])
     else:
       configs.extend(['msaa16', 'nvprmsaa16'])
+  # Runs out of memory on Android bots.
+  if 'Android' not in bot:
+    configs.append('pdf')
 
   # Xoom and NP are running out of RAM when we run all these modes.  skia:3255
   if ('Xoom'        not in bot and