SVG: Fix viewBox animations on shapes with non-scaling-stroke.
<http://webkit.org/b/115173>

Source/WebCore:

From Blink r149058 by <pdr@chromium.org>:

Previously hasAttribute() to determine if a viewBox was set in the transform
code for non-scaling-strokes. hasAttribute() should not be used in this case,
as it will return false if the attribute is not set but the value is animating.

This patch switches to checking if the viewBox is empty instead of checking for
the presence of the attribute.

Test: svg/stroke/animated-non-scaling-stroke.html

* svg/SVGSVGElement.cpp:
(WebCore::SVGSVGElement::localCoordinateSpaceTransform):
* svg/SVGSVGElement.h:
(WebCore::SVGSVGElement::hasEmptyViewBox):

LayoutTests:

From Blink r149058 by <pdr@chromium.org>.

* svg/stroke/animated-non-scaling-stroke-expected.html: Added.
* svg/stroke/animated-non-scaling-stroke.html: Added.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@149102 268f45cc-cd09-0410-ab3c-d52691b4dbfc