Exclude ChromeOS directories from Mac coverage lines....

build/linux/chrome_linux.croc

 # -*- python -*-
 # Crocodile config file for Chromium linux
 
 # TODO(jhawkins): We'll need to add a chromeos.croc once we get a coverage bot
 # for that platform.
 
 {
   # List of rules, applied in order
   'rules' : [
     # Specify inclusions before exclusions, since rules are in order.
 
     # Don't include non-Linux platform dirs
     {
       'regexp' : '.*/(chromeos|views)/',
       'include' : 0,
     },
-    # Don't include windows or mac specific files
+    # Don't include chromeos, windows, or mac specific files
     {
-      'regexp' : '.*(_|/)(mac|win|views)(\\.|_)',
+      'regexp' : '.*(_|/)(chromeos|mac|win|views)(\\.|_)',
       'include' : 0,
     },
 
     # Groups
     {
       'regexp' : '.*_test_linux\\.',
       'group' : 'test',
     },
   ],
 }