IDL compiler: [Reflect, URL] DOMString attributes on Node interfaces

Minor followup:
[URL] disables special treatment in getter; add check for this.

Followup to:
IDL compiler: [Reflect] DOMString attributes on Node interfaces
https://codereview.chromium.org/131063005/

BUG=239771
R=haraken
NOTRY=true

Review URL: https://codereview.chromium.org/132283005

git-svn-id: svn://svn.chromium.org/blink/trunk@164858 bbb929c8-8fbe-4397-9dbb-9b2b20218538