Add support for patternUnits attribute.

The patternUnits attribute defines how a pattern's coordinate system is
defined (x, y, width, height). This is particularly important when using
repeatable patterns in SVG. This commit adds this attribute to the lists
of known properties.

Closes #1548

src/browser/ui/dom/SVGDOMPropertyConfig.js

@@ -37,6 +37,7 @@ var SVGDOMPropertyConfig = {
     gradientTransform: MUST_USE_ATTRIBUTE,
     gradientUnits: MUST_USE_ATTRIBUTE,
     offset: MUST_USE_ATTRIBUTE,
+    patternUnits: MUST_USE_ATTRIBUTE,
     points: MUST_USE_ATTRIBUTE,
     preserveAspectRatio: MUST_USE_ATTRIBUTE,
     r: MUST_USE_ATTRIBUTE,
@@ -63,6 +64,7 @@ var SVGDOMPropertyConfig = {
   DOMAttributeNames: {
     gradientTransform: 'gradientTransform',
     gradientUnits: 'gradientUnits',
+    patternUnits: 'patternUnits',
     preserveAspectRatio: 'preserveAspectRatio',
     spreadMethod: 'spreadMethod',
     stopColor: 'stop-color',