Disable sync for default apps

chrome/browser/extensions/extension_prefs.h

Index: chrome/browser/extensions/extension_prefs.h
diff --git a/chrome/browser/extensions/extension_prefs.h b/chrome/browser/extensions/extension_prefs.h
index 6a7a7d7dae82137980d45e0c1c76743800ad0a71..7da47b69f3ee9c59133d51349d856ca2b62cbae4 100644
--- a/chrome/browser/extensions/extension_prefs.h
+++ b/chrome/browser/extensions/extension_prefs.h
@@ -429,6 +429,9 @@ class ExtensionPrefs : public ContentSettingsStore::Observer,
   // bookmark.
   bool IsFromBookmark(const std::string& extension_id) const;
 
+  // Returns true if the extension was installed as a default app.
+  bool WasInstalledByDefault(const std::string& extension_id) const;
+
   // Helper method to acquire the installation time of an extension.
   // Returns base::Time() if the installation time could not be parsed or
   // found.