Make getLineDash return [] instead of null if it has not yet been set.

tools/dom/scripts/htmlrenamer.py

 #!/usr/bin/python
 # Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 # for details. All rights reserved. Use of this source code is governed by a
 # BSD-style license that can be found in the LICENSE file.
 import logging
 import monitored
 import re
 
 typed_array_renames = {
     'ArrayBuffer': 'ByteBuffer',
@@ skipping 163 matching lines @@
 ])
 
 # Members from the standard dom that should not be exposed publicly in dart:html
 # but need to be exposed internally to implement dart:html on top of a standard
 # browser. They are exposed simply by placing an underscore in front of the
 # name.
 private_html_members = monitored.Set('htmlrenamer.private_html_members', [
   'AudioNode.connect',
   'CanvasRenderingContext2D.arc',
   'CanvasRenderingContext2D.drawImage',
+  'CanvasRenderingContext2D.getLineDash',
   'CSSStyleDeclaration.getPropertyValue',
   'CSSStyleDeclaration.setProperty',
   'CSSStyleDeclaration.var',
   'CompositionEvent.initCompositionEvent',
   'CustomEvent.detail',
   'CustomEvent.initCustomEvent',
   'DeviceOrientationEvent.initDeviceOrientationEvent',
   'Document.createElement',
   'Document.createEvent',
   'Document.createNodeIterator',
@@ skipping 749 matching lines @@
 
     # We're looking for a sequence of letters which start with capital letter
     # then a series of caps and finishes with either the end of the string or
     # a capital letter.
     # The [0-9] check is for names such as 2D or 3D
     # The following test cases should match as:
     #   WebKitCSSFilterValue: WebKit(C)(SS)(F)ilterValue
     #   XPathNSResolver: (X)()(P)ath(N)(S)(R)esolver (no change)
     #   IFrameElement: (I)()(F)rameElement (no change)
     return re.sub(r'([A-Z])([A-Z]{2,})([A-Z]|$)', toLower, name)