We should use UserID object to identify users instead of username.

chrome/browser/ui/webui/options/chromeos/user_image_source.cc

Index: chrome/browser/ui/webui/options/chromeos/user_image_source.cc
diff --git a/chrome/browser/ui/webui/options/chromeos/user_image_source.cc b/chrome/browser/ui/webui/options/chromeos/user_image_source.cc
index ba0082303e13778589fd5ab0cf3f01a06fe3781f..d82481d2378a93acdcdf6406e9476483a545a16b 100644
--- a/chrome/browser/ui/webui/options/chromeos/user_image_source.cc
+++ b/chrome/browser/ui/webui/options/chromeos/user_image_source.cc
@@ -8,6 +8,7 @@
 #include "base/message_loop/message_loop.h"
 #include "base/strings/string_split.h"
 #include "chrome/common/url_constants.h"
+#include "components/user_manager/user_id.h"
 #include "components/user_manager/user_image/default_user_images.h"
 #include "components/user_manager/user_manager.h"
 #include "grit/theme_resources.h"
@@ -37,10 +38,10 @@ namespace options {
 
 // Static.
 base::RefCountedMemory* UserImageSource::GetUserImage(
-    const std::string& email,
+    const user_manager::UserID& user_id,
     ui::ScaleFactor scale_factor) {
   const user_manager::User* user =
-      user_manager::UserManager::Get()->FindUser(email);
+      user_manager::UserManager::Get()->FindUser(user_id);
   if (user) {
     if (user->has_raw_image()) {
       return new base::RefCountedBytes(user->raw_image());
@@ -78,7 +79,7 @@ void UserImageSource::StartDataRequest(
   std::string email;
   GURL url(chrome::kChromeUIUserImageURL + path);
   ParseRequest(url, &email);
-  callback.Run(GetUserImage(email, ui::SCALE_FACTOR_100P));
+  callback.Run(GetUserImage(user_manager::UserID::FromUserEmail(email), ui::SCALE_FACTOR_100P));
 }
 
 std::string UserImageSource::GetMimeType(const std::string& path) const {