Modal window in user session not blocks user adding screen.

ash/test/ash_test_base.h

Index: ash/test/ash_test_base.h
diff --git a/ash/test/ash_test_base.h b/ash/test/ash_test_base.h
index 830001ccc8af382d07a12013b285322ad35cd94f..37453cbb15c08fac675d9228d8d4ae557f7119a8 100644
--- a/ash/test/ash_test_base.h
+++ b/ash/test/ash_test_base.h
@@ -95,6 +95,14 @@ class AshTestBase : public testing::Test {
   aura::test::EventGenerator& GetEventGenerator();
 
  protected:
+  enum UserSessionBlockReason {
+    FIRST_BLOCK_REASON,
+    BLOCKED_BY_LOCK_SCREEN = FIRST_BLOCK_REASON,
+    BLOCKED_BY_LOGIN_SCREEN,
+    BLOCKED_BY_USER_ADDING_SCREEN,
+    NUMBER_OF_BLOCK_REASONS
+  };
+
   // True if the running environment supports multiple displays,
   // or false otherwise (e.g. win8 bot).
   static bool SupportsMultipleDisplays();
@@ -110,6 +118,12 @@ class AshTestBase : public testing::Test {
   void SetSessionStarted(bool session_started);
   void SetUserLoggedIn(bool user_logged_in);
   void SetCanLockScreen(bool can_lock_screen);
+  void SetUserAddingScreenRunning(bool user_adding_screen_running);
+
+  // Methods to emulate blocking and unblocking user session with given
+  // |block_reason|.
+  void BlockUserSession(UserSessionBlockReason block_reason);
+  void UnblockUserSession();
 
  private:
   bool setup_called_;