Add --serial mode to dm, runs unit tests serially

infra/bots/recipes/swarm_test.py

Index: infra/bots/recipes/swarm_test.py
diff --git a/infra/bots/recipes/swarm_test.py b/infra/bots/recipes/swarm_test.py
index 5b9d993f2e6733ae10008b862c9eb2ab2f42db37..636beda2644d61572e9103d5880141e1385b2fde 100644
--- a/infra/bots/recipes/swarm_test.py
+++ b/infra/bots/recipes/swarm_test.py
@@ -320,6 +320,13 @@ def dm_flags(bot):
   if 'TSAN' in bot:
     match.extend(['~ReadWriteAlpha'])   # Flaky on TSAN-covered on nvidia bots.
 
+  if 'x86_64' in bot or 'Arm64' in bot: # Only run test on 32-bit bots.
+    match.append('~ColorSpaceCRBug')
+
+  # For memory intensive tests that we don't want to run multi-threaded.
+  solo = []
+  solo.append('ColorSpaceCRBug')
+
   if blacklist:
     args.append('--blacklist')
     args.extend(blacklist)
@@ -328,6 +335,10 @@ def dm_flags(bot):
     args.append('--match')
     args.extend(match)
 
+  if solo:
+    args.append('--solo')
+    args.extend(solo)
+
   # These bots run out of memory running RAW codec tests. Do not run them in
   # parallel
   if ('NexusPlayer' in bot or 'Nexus5' in bot or 'Nexus9' in bot