Bad position of large operators inside an munderover element

Bad position of large operators inside an munderover element
https://bugs.webkit.org/show_bug.cgi?id=151916

Reviewed by Alejandro G. Castro.

Source/WebCore:

Test: mathml/opentype/large-operators-munderover.html

* rendering/mathml/RenderMathMLOperator.h:
(WebCore::RenderMathMLOperator::isVertical): Expose the direction of the operator.
* rendering/mathml/RenderMathMLUnderOver.cpp:
(WebCore::RenderMathMLUnderOver::layout): Remove call to horizontal stretching for vertical operators.

LayoutTests:

* mathml/opentype/large-operators-munderover-expected.txt: Added.
* mathml/opentype/large-operators-munderover.html: Added.

Add a test to verify the position and size of a large operator used as an munderover base.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@193829 268f45cc-cd09-0410-ab3c-d52691b4dbfc