Rename UserInfo method GetEmail to GetDisplayEmail.

ash/common/system/user/tray_user_unittest.cc

Index: ash/common/system/user/tray_user_unittest.cc
diff --git a/ash/common/system/user/tray_user_unittest.cc b/ash/common/system/user/tray_user_unittest.cc
index 3e77a74d804a33d03a481c68aa9cdf0042b4b821..bef99a38a4e82233ee655a4b50ec6c133f9e0899 100644
--- a/ash/common/system/user/tray_user_unittest.cc
+++ b/ash/common/system/user/tray_user_unittest.cc
@@ -258,8 +258,10 @@ TEST_F(TrayUserTest, MutiUserModeButtonClicks) {
   EXPECT_EQ(active_user->GetAccountId(), second_user->GetAccountId());
   // Since the name is capitalized, the email should be different then the
   // user_id.
-  EXPECT_NE(active_user->GetAccountId().GetUserEmail(),
-            second_user->GetEmail());
+  EXPECT_NE(active_user->GetAccountId(), second_user->GetAccountId())
+      << "User switch failed: active_user:"
+      << active_user->GetAccountId().Serialize()
+      << ", second_user:" << second_user->GetAccountId().Serialize();
   tray()->CloseSystemBubble();
 }