Allow chrome to become the os default handler for arbitrary protocols on mac/win.

chrome/browser/platform_util_mac.mm

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/platform_util.h"
 
 #include <Carbon/Carbon.h>
 #import <Cocoa/Cocoa.h>
 #include <CoreServices/CoreServices.h>
 
@@ skipping 212 matching lines @@
   }
 #endif
 
   return CHANNEL_UNKNOWN;
 }
 
 bool CanSetAsDefaultBrowser() {
   return GetChannel() != CHANNEL_CANARY;
 }
 
+bool CanSetAsDefaultProtocolClient(const std::string& protocol) {
+  return CanSetAsDefaultBrowser();
+}
+
 }  // namespace platform_util