Enable LSan leak checking for ASan bots.

tools-webrtc/mb/mb.py

Index: tools-webrtc/mb/mb.py
diff --git a/tools-webrtc/mb/mb.py b/tools-webrtc/mb/mb.py
index a2a593f95988e0a992675f9e86b49251deffdcba..55ae8ba0bbe4972fe0c05731a493646e50b7cb2a 100755
--- a/tools-webrtc/mb/mb.py
+++ b/tools-webrtc/mb/mb.py
@@ -1105,6 +1105,7 @@ class MetaBuildWrapper(object):
         ]
 
       asan = 'is_asan=true' in vals['gn_args']
+      lsan = 'is_lsan=true' in vals['gn_args']
       msan = 'is_msan=true' in vals['gn_args']
       tsan = 'is_tsan=true' in vals['gn_args']
 
@@ -1124,6 +1125,7 @@ class MetaBuildWrapper(object):
       cmdline.extend([
           '--',
           '--asan=%d' % asan,
+          '--lsan=%d' % lsan,
           '--msan=%d' % msan,
           '--tsan=%d' % tsan,
       ])