SyncService::CanSyncFeatureStart: Also check IsAuthenticatedAccountPrimary

Sync-the-feature requires a primary account, so this is more accurate.

Bug: 871221
Change-Id: Iadd226c28d0d82cc86640a3c210f95505a219465
Reviewed-on: https://chromium-review.googlesource.com/c/1339939
Commit-Queue: Marc Treib <treib@chromium.org>
Reviewed-by: Mikel Astiz <mastiz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#608774}

components/sync/driver/sync_service.cc

@@ -17,12 +17,12 @@ bool SyncService::IsSyncFeatureEnabled() const {
   // Note: IsFirstSetupComplete() shouldn't usually be true if we don't have a
   // primary account, but it could happen if the account changes from primary to
   // secondary.
-  return GetDisableReasons() == DISABLE_REASON_NONE && IsFirstSetupComplete() &&
-         IsAuthenticatedAccountPrimary();
+  return CanSyncFeatureStart() && IsFirstSetupComplete();
 }
 
 bool SyncService::CanSyncFeatureStart() const {
-  return GetDisableReasons() == DISABLE_REASON_NONE;
+  return GetDisableReasons() == DISABLE_REASON_NONE &&
+         IsAuthenticatedAccountPrimary();
 }
 
 bool SyncService::IsEngineInitialized() const {

components/sync/driver/sync_service.h

@@ -188,8 +188,10 @@ class SyncService : public DataTypeEncryptionHandler, public KeyedService {
   // Sync-the-feature is disabled by the user, by enterprise policy, etc.
   bool IsEngineInitialized() const;
 
-  // Equivalent to having no disable reasons, i.e.
-  // "GetDisableReasons() == DISABLE_REASON_NONE".
+  // Returns whether Sync-the-feature can (attempt to) start. This means that
+  // there is a primary account and no disable reasons. It does *not* require
+  // first-time Sync setup to be complete, because that can only happen after
+  // the engine has started.
   // Note: This refers to Sync-the-feature. Sync-the-transport may be running
   // even if this is false.
   bool CanSyncFeatureStart() const;