Don't modify shared style objects in RenderMathMLRoot.cpp

Don't modify shared style objects in RenderMathMLRoot.cpp
https://bugs.webkit.org/show_bug.cgi?id=83736

Patch by David Barton <dbarton@mathscribe.com> on 2012-04-12
Reviewed by Julien Chaffraix.

Source/WebCore:

To leave room for the radical sign and absolutely positioned "index", we switch to using
intrinsic padding. RenderMathMLRoot.cpp is also cleaned up and prepared for merging with
RenderMathMLSquareRoot.cpp. The base and index are no longer wrapped in extra renderers,
and the child renderers are now in the same order as in the DOM. Some padding/placement
terms are unified and debugged.

Tested by existing tests in roots.xhtml.

* css/mathml.css:
(mroot):
(mroot > * + *):
(mroot > * + mrow, mroot > * + mfenced):
* rendering/mathml/RenderMathMLRoot.cpp:
(WebCore):
(WebCore::RenderMathMLRoot::index):
(WebCore::RenderMathMLRoot::paint):
(WebCore::RenderMathMLRoot::layout):
* rendering/mathml/RenderMathMLRoot.h:
(RenderMathMLRoot):
* rendering/mathml/RenderMathMLSquareRoot.cpp:
(WebCore):
(WebCore::RenderMathMLSquareRoot::paint):

LayoutTests:

* platform/mac/mathml/presentation/roots-expected.png:
* platform/mac/mathml/presentation/roots-expected.txt:

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@114012 268f45cc-cd09-0410-ab3c-d52691b4dbfc