Underlines are too thick when zoomed in

Underlines are too thick when zoomed in
https://bugs.webkit.org/show_bug.cgi?id=129352

Reviewed by Dean Jackson.

Source/WebCore:

The input to the underline drawing code is in user-space, not device-space.
The underlines were getting scaled twice, once in InlineTextBox and the other
in GraphicsContext.

Test: fast/css3-text/css3-text-decoration/text-decoration-scaled.html

* rendering/InlineTextBox.cpp:
(WebCore::InlineTextBox::paintDecoration):

LayoutTests:

This test changes the page scale factor to a very large value, simulating
the user zooming in with a trackpad. It then positions the viewport
to a place where the underline should not be drawn. It then compares this
to a completely white page.

This explanation cannot be in the test itself because the test sets the
scale factor too high for the tester to be able to read text.

* fast/css3-text/css3-text-decoration/text-decoration-scaled-expected.html: Added.
* fast/css3-text/css3-text-decoration/text-decoration-scaled.html: Added.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@164741 268f45cc-cd09-0410-ab3c-d52691b4dbfc