This CL replaces user_manager::UserID with AccountId.

ash/test/test_session_state_delegate.cc

Index: ash/test/test_session_state_delegate.cc
diff --git a/ash/test/test_session_state_delegate.cc b/ash/test/test_session_state_delegate.cc
index 7f2e648d3796a15a18fddb4747b84919cf47ce81..e0f6b610f68f3409acffa4fe88c579a661a3c002 100644
--- a/ash/test/test_session_state_delegate.cc
+++ b/ash/test/test_session_state_delegate.cc
@@ -12,6 +12,7 @@
 #include "base/stl_util.h"
 #include "base/strings/string16.h"
 #include "base/strings/utf_string_conversions.h"
+#include "components/signin/core/account_id/account_id.h"
 #include "components/user_manager/user_info.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
@@ -21,17 +22,19 @@ namespace test {
 namespace {
 
 // The the "canonicalized" user ID from a given |email| address.
-std::string GetUserIDFromEmail(const std::string& email) {
+AccountId GetAccountIdFromEmail(const std::string& email) {
   std::string user_id = email;
   std::transform(user_id.begin(), user_id.end(), user_id.begin(), ::tolower);
-  return user_id;
+  return AccountId::FromUserEmail(user_id);
 }
 
 }  // namespace
 
 class MockUserInfo : public user_manager::UserInfo {
  public:
-  explicit MockUserInfo(const std::string& id) : email_(id) {}
+  explicit MockUserInfo(const std::string& display_email)
+      : display_email_(display_email),

[stevenjb, 2015/10/23 17:17:02]

Don't store display_email_ separately, there is the possibility of it getting
out of sunc, just have GetEmail() return the email from account_id_. (I know
it's just a test delegate, but still...)

[Alexander Alekseev, 2015/10/23 23:21:22]

Display Email must be different from account id, this is what it all is for ;)

[stevenjb, 2015/10/26 18:28:00]

Acknowledged.

+        account_id_(GetAccountIdFromEmail(display_email)) {}
   ~MockUserInfo() override {}
 
   void SetUserImage(const gfx::ImageSkia& user_image) {
@@ -46,18 +49,17 @@ class MockUserInfo : public user_manager::UserInfo {
     return base::UTF8ToUTF16("Über Über Über Über");
   }
 
-  std::string GetEmail() const override { return email_; }
+  std::string GetEmail() const override { return display_email_; }
 
-  std::string GetUserID() const override {
-    return GetUserIDFromEmail(GetEmail());
-  }
+  AccountId GetAccountId() const override { return account_id_; }
 
   const gfx::ImageSkia& GetImage() const override { return user_image_; }
 
   // A test user image.
   gfx::ImageSkia user_image_;
 
-  std::string email_;
+  std::string display_email_;
+  AccountId account_id_;
 
   DISALLOW_COPY_AND_ASSIGN(MockUserInfo);
 };
@@ -215,18 +217,19 @@ gfx::ImageSkia TestSessionStateDelegate::GetAvatarImageForWindow(
 }
 
 void TestSessionStateDelegate::SwitchActiveUser(const std::string& user_id) {
+  const AccountId account_id(GetAccountIdFromEmail(user_id));
   // Make sure this is a user id and not an email address.
-  EXPECT_EQ(user_id, GetUserIDFromEmail(user_id));
+  EXPECT_EQ(user_id, account_id.GetUserEmail());
   active_user_index_ = 0;
   for (std::vector<MockUserInfo*>::iterator iter = user_list_.begin();
        iter != user_list_.end();
        ++iter) {
-    if ((*iter)->GetUserID() == user_id) {
+    if ((*iter)->GetAccountId() == account_id) {
       active_user_index_ = iter - user_list_.begin();
       return;
     }
   }
-  NOTREACHED() << "Unknown user:" << user_id;
+  NOTREACHED() << "Unknown user:" << account_id.GetUserEmail();
 }
 
 void TestSessionStateDelegate::CycleActiveUser(CycleUser cycle_user) {