cros: Increase maximum number of users on login screen

The limitation is outdated and there is no reason to limit it anymore.
Setting the limit to 50 to have sensible scroll view of users.

This has nothing to do with the disk space exhaustion. That handled
separetely.

Fixed: 1040890
Change-Id: Ib13d065f55cc9cc1d1d6f65a2b4db9d65805bb61
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2041442
Commit-Queue: Roman Sorokin [CET] <rsorokin@chromium.org>
Commit-Queue: Denis Kuznetsov [CET] <antrim@chromium.org>
Auto-Submit: Roman Sorokin [CET] <rsorokin@chromium.org>
Reviewed-by: Denis Kuznetsov [CET] <antrim@chromium.org>
Cr-Commit-Position: refs/heads/master@{#738933}

chrome/browser/chromeos/login/screens/user_selection_screen.cc

@@ -85,7 +85,7 @@ const char kKeyAllowFingerprint[] = "allowFingerprint";
 
 // Max number of users to show.
 // Please keep synced with one in signin_userlist_unittest.cc.
-const size_t kMaxUsers = 18;
+const size_t kMaxUsers = 50;
 
 const int kPasswordClearTimeoutSec = 60;
 

chrome/browser/ui/webui/chromeos/login/signin_userlist_unittest.cc

@@ -7,6 +7,7 @@
 #include "base/compiler_specific.h"
 #include "base/memory/ptr_util.h"
 #include "base/stl_util.h"
+#include "base/strings/string_number_conversions.h"
 #include "chrome/browser/chromeos/login/screens/user_selection_screen.h"
 #include "chrome/browser/chromeos/login/users/fake_chrome_user_manager.h"
 #include "chrome/browser/chromeos/login/users/multi_profile_user_controller.h"
@@ -23,15 +24,13 @@
 
 namespace {
 
-const size_t kMaxUsers = 18; // same as in user_selection_screen.cc
+const size_t kMaxUsers = 50;  // same as in user_selection_screen.cc
 const char* kOwner = "owner@gmail.com";
 const char* kUsersPublic[] = {"public0@gmail.com", "public1@gmail.com"};
-const char* kUsers[] = {
-    "a0@gmail.com", "a1@gmail.com", "a2@gmail.com", "a3@gmail.com",
-    "a4@gmail.com", "a5@gmail.com", "a6@gmail.com", "a7@gmail.com",
-    "a8@gmail.com", "a9@gmail.com", "a10@gmail.com", "a11@gmail.com",
-    "a12@gmail.com", "a13@gmail.com", "a14@gmail.com", "a15@gmail.com",
-    "a16@gmail.com", "a17@gmail.com", kOwner, "a18@gmail.com"};
+
+std::string GenerateUserEmail(int number) {
+  return "a" + base::NumberToString(number) + "@gmail.com";
+}
 
 }  // namespace
 
@@ -60,8 +59,13 @@ class SigninPrepareUserListTest : public testing::Test,
       fake_user_manager_->AddPublicAccountUser(
           AccountId::FromUserEmail(kUsersPublic[i]));
 
-    for (size_t i = 0; i < base::size(kUsers); ++i)
-      fake_user_manager_->AddUser(AccountId::FromUserEmail(kUsers[i]));
+    for (size_t i = 0; i < kMaxUsers + 1; ++i) {
+      fake_user_manager_->AddUser(
+          AccountId::FromUserEmail(GenerateUserEmail(i)));
+      // Insert owner second to last.
+      if (i == kMaxUsers - 1)
+        fake_user_manager_->AddUser(AccountId::FromUserEmail(kOwner));
+    }
 
     fake_user_manager_->set_owner_id(AccountId::FromUserEmail(kOwner));
   }
@@ -106,7 +110,7 @@ TEST_F(SigninPrepareUserListTest, AlwaysKeepOwnerInList) {
       true /* is_signin_to_add */);
 
   EXPECT_EQ(kMaxUsers, users_to_send.size());
-  EXPECT_EQ("a18@gmail.com",
+  EXPECT_EQ(GenerateUserEmail(kMaxUsers),
             users_to_send.back()->GetAccountId().GetUserEmail());
   EXPECT_EQ(kOwner,
             users_to_send[kMaxUsers - 2]->GetAccountId().GetUserEmail());