Android: further "user build" perf test automation.

build/android/pylib/android_commands.py

Index: build/android/pylib/android_commands.py
diff --git a/build/android/pylib/android_commands.py b/build/android/pylib/android_commands.py
index a4340b2a5d64384e881b52f5c7c3547e18e68c44..7a8c5e5687ec501088a8d7886a29aa2d7dc11ce8 100644
--- a/build/android/pylib/android_commands.py
+++ b/build/android/pylib/android_commands.py
@@ -729,7 +729,8 @@ class AndroidCommands(object):
     Devices running user builds don't have adb root, but may provide "su" which
     can be used for accessing protected files.
     """
-    return self.RunShellCommand('su -c cat /dev/null') == ['']
+    r = self.RunShellCommand('su -c cat /dev/null')
+    return r == [] or r[0].strip() == ''
 
   def GetProtectedFileContents(self, filename, log_result=False):
     """Gets contents from the protected file specified by |filename|.