Preventing our default handlers for ChromeOS to show up or confuse the user

chrome/browser/custom_handlers/protocol_handler_registry.h

Index: chrome/browser/custom_handlers/protocol_handler_registry.h
diff --git a/chrome/browser/custom_handlers/protocol_handler_registry.h b/chrome/browser/custom_handlers/protocol_handler_registry.h
index edfb7ab6327372f319afaec84e7d5fe26b2650a6..c4ed21be65bcec939147715d58892ea423b34def 100644
--- a/chrome/browser/custom_handlers/protocol_handler_registry.h
+++ b/chrome/browser/custom_handlers/protocol_handler_registry.h
@@ -194,6 +194,9 @@ class ProtocolHandlerRegistry
  private:
   friend class base::RefCountedThreadSafe<ProtocolHandlerRegistry>;
 
+  // Install the default handlers.
+  void InstallFixedHandlers();
+
   // Puts the given handler at the top of the list of handlers for its
   // protocol.
   void PromoteHandler(const ProtocolHandler& handler);
@@ -277,6 +280,10 @@ class ProtocolHandlerRegistry
   // Whether or not we are loading.
   bool is_loading_;
 
+  // Once predefined defaults are set, this will be set and an overwrite of
+  // them won't be possible anymore.
+  bool fixed_handlers_loaded_;
+
   DefaultClientObserverList default_client_observers_;
 
   // Copy of default_handlers_ that is only accessed on the IO thread.