This CL replaces e-mail with AccountId on user selection screen.

components/login/base_screen_handler_utils.cc

Index: components/login/base_screen_handler_utils.cc
diff --git a/components/login/base_screen_handler_utils.cc b/components/login/base_screen_handler_utils.cc
index 6454cdf87b2a1d70dd8f899ff0c4ef31352852dd..fd977a33eaa943eb2b2170b280ae12f0579f9945 100644
--- a/components/login/base_screen_handler_utils.cc
+++ b/components/login/base_screen_handler_utils.cc
@@ -4,6 +4,8 @@
 
 #include "components/login/base_screen_handler_utils.h"
 
+#include "components/signin/core/account_id/account_id.h"
+
 namespace login {
 
 namespace {
@@ -56,6 +58,20 @@ bool ParseValue(const base::Value* value, String16List* out_value) {
   return ParseStringList(value, out_value);
 }
 
+bool ParseValue(const base::Value* value, AccountId* out_value) {
+  std::string serialized;
+  const bool has_string = value->GetAsString(&serialized);
+  if (!has_string)
+    return false;
+
+  if (AccountId::Deserialize(serialized, out_value))
+    return true;
+
+  LOG(ERROR) << "Failed to deserialize '" << serialized << "'";
+  *out_value = AccountId::FromUserEmail(serialized);
+  return true;
+}
+
 base::FundamentalValue MakeValue(bool v) {
   return base::FundamentalValue(v);
 }
@@ -76,4 +92,11 @@ base::StringValue MakeValue(const base::string16& v) {
   return base::StringValue(v);
 }
 
+base::StringValue MakeValue(const AccountId& v) {
+  return base::StringValue(v.Serialize());
+}
+
+ParsedValueContainer<AccountId>::ParsedValueContainer() {
+}
+
 }  // namespace login