Subpixel layout: Default style of input type=checkbox/radio (0.5ex) adds 1px extra...

Subpixel layout: Default style of input type=checkbox/radio (0.5ex) adds 1px extra margin on both left and right.
https://bugs.webkit.org/show_bug.cgi?id=125728

Reviewed by Simon Fraser.

Using the 0.5ex value to set checkbox/radio left and right margins is a long-standing
(khtml) behavior. While it indicates dynamic behavior, in order to get the margins changed,
the widget's font size needs to be set, which is rather rare for such input types.
It also results in odd layout, where the checkbox's indentation may seem to change randomly.

'<input style="font-size: 30px;" type="checkbox">foo' changes neither the checkbox
nor the text size, but it indents the line by about 15px.

Other browsers (FF, Opera with Presto) disagree and they set static margins values.
2px is the current default computed value.

Source/WebCore:

* css/html.css:
(input[type="radio"], input[type="checkbox"]):

LayoutTests:

* platform/mac-mountainlion/fast/block/margin-collapse/103-expected.txt:
* platform/mac-mountainlion/fast/forms/basic-inputs-expected.txt:
* platform/mac-mountainlion/fast/forms/box-shadow-override-expected.txt:
* platform/mac-mountainlion/fast/forms/form-element-geometry-expected.txt:
* platform/mac-mountainlion/fast/forms/input-appearance-height-expected.txt:
* platform/mac-mountainlion/fast/forms/input-value-expected.txt:
* platform/mac-mountainlion/fast/replaced/replaced-breaking-expected.txt:
* platform/mac-mountainlion/fast/text/textIteratorNilRenderer-expected.txt:
* platform/mac-mountainlion/http/tests/navigation/javascriptlink-frames-expected.txt:
* platform/mac-mountainlion/tables/mozilla/bugs/bug4527-expected.txt:
* platform/mac/compositing/overflow/theme-affects-visual-overflow-expected.txt:
* platform/mac/css1/box_properties/acid_test-expected.txt:
* platform/mac/css2.1/t09-c5526c-display-00-e-expected.txt:
* platform/mac/css3/selectors3/html/css3-modsel-25-expected.txt:
* platform/mac/css3/selectors3/html/css3-modsel-70-expected.txt:
* platform/mac/css3/selectors3/xhtml/css3-modsel-25-expected.txt:
* platform/mac/css3/selectors3/xhtml/css3-modsel-70-expected.txt:
* platform/mac/css3/selectors3/xml/css3-modsel-25-expected.txt:
* platform/mac/css3/selectors3/xml/css3-modsel-70-expected.txt:
* platform/mac/fast/block/basic/011-expected.txt:
* platform/mac/fast/block/margin-collapse/103-expected.txt:
* platform/mac/fast/css/non-standard-checkbox-size-expected.txt:
* platform/mac/fast/forms/001-expected.txt:
* platform/mac/fast/forms/basic-inputs-expected.txt:
* platform/mac/fast/forms/box-shadow-override-expected.txt:
* platform/mac/fast/forms/file/file-input-disabled-expected.txt:
* platform/mac/fast/forms/form-element-geometry-expected.txt:
* platform/mac/fast/forms/formmove-expected.txt:
* platform/mac/fast/forms/formmove2-expected.txt:
* platform/mac/fast/forms/indeterminate-expected.txt:
* platform/mac/fast/forms/input-appearance-height-expected.txt:
* platform/mac/fast/forms/input-value-expected.txt:
* platform/mac/fast/inline/positionedLifetime-expected.txt:
* platform/mac/fast/parser/bad-xml-slash-expected.txt:
* platform/mac/fast/replaced/replaced-breaking-expected.txt:
* platform/mac/fast/replaced/width100percent-checkbox-expected.txt:
* platform/mac/fast/replaced/width100percent-radio-expected.txt:
* platform/mac/fast/text/textIteratorNilRenderer-expected.txt:
* platform/mac/fast/text/whitespace/normal-after-nowrap-breaking-expected.txt:
* platform/mac/http/tests/navigation/javascriptlink-frames-expected.txt:
* platform/mac/tables/mozilla/bugs/bug1318-expected.txt:
* platform/mac/tables/mozilla/bugs/bug4527-expected.txt:
* platform/mac/tables/mozilla_expected_failures/core/captions1-expected.txt:
* platform/mac/tables/mozilla_expected_failures/core/captions2-expected.txt:

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@162742 268f45cc-cd09-0410-ab3c-d52691b4dbfc