Make shrink-wrapping test a ref-test instead of pixel-test

Make shrink-wrapping test a ref-test instead of pixel-test
https://bugs.webkit.org/show_bug.cgi?id=147081

Reviewed by Sam Weinig.

Source/WebCore:

Nobody runs pixel tests.

* svg/SVGPathUtilities.cpp:
(WebCore::pathIteratorForBuildingString):
(WebCore::buildStringFromPath):
* svg/SVGPathUtilities.h:
Add a helper that turns a Path into a SVG path string.

* testing/Internals.cpp:
(WebCore::Internals::pathStringWithShrinkWrappedRects):
* testing/Internals.h:
* testing/Internals.idl:
Have the internals shrink-wrap method return an SVG path instead of a DOMPath.

LayoutTests:

* fast/shrink-wrap/rect-shrink-wrap-expected.html: Added.
* fast/shrink-wrap/rect-shrink-wrap-expected.png: Removed.
* fast/shrink-wrap/rect-shrink-wrap-expected.txt: Removed.
* fast/shrink-wrap/rect-shrink-wrap.html:
SVG all the things.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@187018 268f45cc-cd09-0410-ab3c-d52691b4dbfc