Install default apps if sync is disabled.

chrome/browser/extensions/external_pref_loader.h

Index: chrome/browser/extensions/external_pref_loader.h
diff --git a/chrome/browser/extensions/external_pref_loader.h b/chrome/browser/extensions/external_pref_loader.h
index dca6dad985035cc5f02eb498fbb619e2c9e1d7f1..d951db8709b6c763aafdd3021c9ba7f9bef35342 100644
--- a/chrome/browser/extensions/external_pref_loader.h
+++ b/chrome/browser/extensions/external_pref_loader.h
@@ -13,6 +13,8 @@
 #include "base/values.h"
 #include "chrome/browser/extensions/external_loader.h"
 #include "chrome/browser/prefs/pref_service_syncable_observer.h"
+#include "chrome/browser/sync/profile_sync_service.h"
+#include "chrome/browser/sync/profile_sync_service_observer.h"
 
 class PrefServiceSyncable;
 class Profile;
@@ -24,7 +26,8 @@ namespace extensions {
 // Instances of this class are expected to be created and destroyed on the UI
 // thread and they are expecting public method calls from the UI thread.
 class ExternalPrefLoader : public ExternalLoader,
-                           public PrefServiceSyncableObserver {
+                           public PrefServiceSyncableObserver,
+                           public ProfileSyncServiceObserver {
  public:
   enum Options {
     NONE = 0,
@@ -67,9 +70,15 @@ class ExternalPrefLoader : public ExternalLoader,
   // PrefServiceSyncableObserver:
   void OnIsSyncingChanged() override;
 
+  // ProfileSyncServiceObserver
+  void OnStateChanged() override;
+
   // If priority sync ready posts LoadOnFileThread and return true.
   bool PostLoadIfPrioritySyncReady();
 
+  // Post LoadOnFileThread and stop observing for sync service states.
+  void PostLoadAndRemoveObservers();
+
   // Actually searches for and loads candidate standalone extension preference
   // files in the path corresponding to |base_path_id|.
   // Must be called on the file thread.