Prevent mouse from getting stuck on second display in login

ash/test/ash_test_helper.h

Index: ash/test/ash_test_helper.h
diff --git a/ash/test/ash_test_helper.h b/ash/test/ash_test_helper.h
index 669ec292f15f1f4febe0d85c8f92cbafc17f2ed8..f4d7706469f31429ebab9e0d413cbcfc28b5aafa 100644
--- a/ash/test/ash_test_helper.h
+++ b/ash/test/ash_test_helper.h
@@ -33,7 +33,9 @@ class AshTestHelper {
   ~AshTestHelper();
 
   // Creates the ash::Shell and performs associated initialization.
-  void SetUp();
+  // Set |start_session| to true if the user should log in before
+  // the test is run.
+  void SetUp(bool start_session);
 
   // Destroys the ash::Shell and performs associated cleanup.
   void TearDown();