Updated SVGListPropertyHelper as per SVG2 Spec

LayoutTests/TestExpectations

Index: LayoutTests/TestExpectations
diff --git a/LayoutTests/TestExpectations b/LayoutTests/TestExpectations
index 22d1c2b974a4a3dc4c764931ccdb84d29a2eccaf..ee00550d09ee20cf6471586ef57a6606ebc83ad3 100644
--- a/LayoutTests/TestExpectations
+++ b/LayoutTests/TestExpectations
@@ -702,6 +702,16 @@ crbug.com/271243 http/tests/misc/acid3.html [ Pass Failure ]
 
 crbug.com/278497 [ Mac Win ] http/tests/security/contentSecurityPolicy/1.1/plugintypes-invalid.html [ Failure Pass  ]
 
+crbug.com/497196 svg/dom/SVGLengthList-appendItem.xhtml [ NeedsRebaseline ]

[fs, 2015/06/17 16:02:04]

I'd prefer if these weren't needed - I could only notice one visual difference
(square -> triangle) and would prefer the test to be fixed in that case instead
(it bad that these tests have visual output in the first place =/)

[Shanmuga Pandi, 2015/06/18 11:30:45]

Actually there are differences in the expected png files. If you observe closely
you can find the difference in scroll bar thumb size, since the no of text lines
are increased.

[fs, 2015/06/18 12:57:22]

Ok, that sucks.

+crbug.com/497196 svg/dom/SVGLengthList-initialize.xhtml [ NeedsRebaseline ]
+crbug.com/497196 svg/dom/SVGLengthList-insertItemBefore.xhtml [ NeedsRebaseline ]
+crbug.com/497196 svg/dom/SVGLengthList-removeItem.xhtml [ NeedsRebaseline ]
+crbug.com/497196 svg/dom/SVGLengthList-replaceItem.xhtml [ NeedsRebaseline ]
+crbug.com/497196 svg/dom/SVGPathSegList-appendItem.xhtml [ NeedsRebaseline ]
+crbug.com/497196 svg/dom/SVGPathSegList-clear-and-initialize.xhtml [ NeedsRebaseline ]
+crbug.com/497196 svg/dom/SVGPathSegList-insertItemBefore.xhtml [ NeedsRebaseline ]
+crbug.com/497196 svg/dom/SVGPathSegList-replaceItem.xhtml [ NeedsRebaseline ]
+
 crbug.com/280342 [ Linux Win ] http/tests/media/progress-events-generated-correctly.html [ Failure Pass ]
 crbug.com/282081 [ Win Release ] http/tests/security/contentSecurityPolicy/report-only-from-header.php [ Pass Timeout ]
 crbug.com/282086 [ XP Release ] virtual/gpu/fast/canvas/webgl/gl-uniform-arrays.html [ Pass Timeout ]
@@ -1959,3 +1969,4 @@ crbug.com/495523 [ XP ] svg/W3C-SVG-1.1/extend-namespace-01-f.svg [ Failure ]
 crbug.com/495523 svg/wicd/test-rightsizing-b.xhtml [ Pass Failure ]
 
 crbug.com/495542 [ XP ] plugins/webview-plugin-lifecycle.html [ Failure ]
+