Method returning whether account_id migration is supported

To allow tests to be written without depending on the side-effect
of the initialization of an AccountTrackerService, add a public
method returning whether migration of account_id is supported on
the current platform.

Bug: none
Change-Id: Ibe632d42378ad952ff92645598fc396cda3a2879
Reviewed-on: https://chromium-review.googlesource.com/1188577
Commit-Queue: Sylvain Defresne <sdefresne@chromium.org>
Reviewed-by: David Roger <droger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#586304}

components/signin/core/browser/account_tracker_service.cc

@@ -207,6 +207,15 @@ gfx::Image AccountTrackerService::GetAccountImage(
                                                   : gfx::Image();
 }
 
+// static
+bool AccountTrackerService::IsMigrationSupported() {
+#if defined(OS_CHROMEOS)
+  return false;
+#else
+  return true;
+#endif
+}
+
 AccountTrackerService::AccountIdMigrationState
 AccountTrackerService::GetMigrationState() const {
   return GetMigrationState(pref_service_);
@@ -347,7 +356,9 @@ void AccountTrackerService::SetIsAdvancedProtectionAccount(
 }
 
 bool AccountTrackerService::IsMigratable() const {
-#if !defined(OS_CHROMEOS)
+  if (!IsMigrationSupported())
+    return false;
+
   for (std::map<std::string, AccountState>::const_iterator it =
            accounts_.begin();
        it != accounts_.end(); ++it) {
@@ -356,9 +367,6 @@ bool AccountTrackerService::IsMigratable() const {
       return false;
   }
   return true;
-#else
-  return false;
-#endif
 }
 
 void AccountTrackerService::MigrateToGaiaId() {

components/signin/core/browser/account_tracker_service.h

@@ -129,6 +129,10 @@ class AccountTrackerService : public KeyedService {
 
   void RemoveAccount(const std::string& account_id);
 
+  // Is migration of the account id from normalized email to gaia id supported
+  // on the current platform?
+  static bool IsMigrationSupported();
+
   AccountIdMigrationState GetMigrationState() const;
   void SetMigrationDone();
   static AccountIdMigrationState GetMigrationState(