Bug 1548529 - Remove values "thin", "thick", "medium" values of mfrac…

…linethickness. r=emilio

See w3c/mathml#4
and https://groups.google.com/forum/#!topic/mozilla.dev.platform/G91-vBeC3Rw

This commit introduces a new preference option
mathml.mfrac_linethickness_names.disabled to disable linethickness names. For
now, these names are only disabled in Nightly builds. Announcements and actual
disabling of this and other MathML features will be considered later.

* test_bug553917.html is updated to check that these values now cause an error
  message to be logged into the console.
* mstyle-1.xhtml is updated to use a numeric linethickness since the point of
  the test is just to check that the attribute is not supported on mstyle, not
  about the actual attribute value.
* Other fractions tests relying on linethickness names are executed with the
  proper preference adjustment.
* mathml/presentation-markup/fractions/frac-linethickness-001.html is now
  closer to its expectation ; however the test still fails because nonzero
  unitless values are not removed yet. See
  w3c/mathml#24

Differential Revision: https://phabricator.services.mozilla.com/D42323

UltraBlame original commit: 0692436a2b33c134bf50654ce466e4bd5ddb05cf

layout/mathml/nsMathMLmfracFrame.cpp

@@ -44,6 +44,15 @@ h
 #
 include
 "
+mozilla
+/
+StaticPrefs_mathml
+.
+h
+"
+#
+include
+"
 nsLayoutUtils
 .
 h
@@ -369,6 +378,37 @@ IsEmpty
 {
 if
 (
+StaticPrefs
+:
+:
+mathml_mfrac_linethickness_names_disabled
+(
+)
+)
+{
+lineThickness
+=
+defaultThickness
+;
+ParseNumericValue
+(
+aThicknessAttribute
+&
+lineThickness
+nsMathMLElement
+:
+:
+PARSE_ALLOW_UNITLESS
+aPresContext
+aComputedStyle
+aFontSizeInflation
+)
+;
+}
+else
+{
+if
+(
 aThicknessAttribute
 .
 EqualsLiteral
@@ -407,13 +447,15 @@ defaultThickness
 -
 onePixel
 )
+{
 lineThickness
 =
 defaultThickness
 -
 onePixel
 ;
 }
+}
 else
 if
 (
@@ -464,13 +506,15 @@ defaultThickness
 +
 onePixel
 )
+{
 lineThickness
 =
 defaultThickness
 +
 onePixel
 ;
 }
+}
 else
 {
 lineThickness
@@ -493,6 +537,7 @@ aFontSizeInflation
 ;
 }
 }
+}
 if
 (
 lineThickness

layout/mathml/tests/test_bug553917.html

@@ -716,6 +716,111 @@
 /
 math
 >
+<
+math
+>
+<
+mfrac
+linethickness
+=
+"
+thin
+"
+>
+<
+mn
+>
+1
+<
+/
+mn
+>
+<
+mn
+>
+2
+<
+/
+mn
+>
+<
+/
+mfrac
+>
+<
+/
+math
+>
+<
+math
+>
+<
+mfrac
+linethickness
+=
+"
+medium
+"
+>
+<
+mn
+>
+1
+<
+/
+mn
+>
+<
+mn
+>
+2
+<
+/
+mn
+>
+<
+/
+mfrac
+>
+<
+/
+math
+>
+<
+math
+>
+<
+mfrac
+linethickness
+=
+"
+thick
+"
+>
+<
+mn
+>
+1
+<
+/
+mn
+>
+<
+mn
+>
+2
+<
+/
+mn
+>
+<
+/
+mfrac
+>
+<
+/
+math
+>
 *
 /
 LengthParsingError
@@ -730,6 +835,9 @@
 false
 false
 false
+false
+false
+false
 ]
 args
 :
@@ -769,6 +877,21 @@
 BADdepth
 "
 ]
+[
+"
+thin
+"
+]
+[
+"
+medium
+"
+]
+[
+"
+thick
+"
+]
 ]
 }
 /
@@ -1706,6 +1829,111 @@
 math
 >
 <
+mfrac
+linethickness
+=
+"
+thin
+"
+>
+<
+mn
+>
+1
+<
+/
+mn
+>
+<
+mn
+>
+2
+<
+/
+mn
+>
+<
+/
+mfrac
+>
+<
+/
+math
+>
+<
+math
+>
+<
+mfrac
+linethickness
+=
+"
+medium
+"
+>
+<
+mn
+>
+1
+<
+/
+mn
+>
+<
+mn
+>
+2
+<
+/
+mn
+>
+<
+/
+mfrac
+>
+<
+/
+math
+>
+<
+math
+>
+<
+mfrac
+linethickness
+=
+"
+thick
+"
+>
+<
+mn
+>
+1
+<
+/
+mn
+>
+<
+mn
+>
+2
+<
+/
+mn
+>
+<
+/
+mfrac
+>
+<
+/
+math
+>
+<
+math
+>
+<
 mmultiscripts
 >
 <

layout/reftests/mathml/mstyle-1.xhtml

@@ -350,7 +350,7 @@ true
 linethickness
 =
 "
-thick
+10px
 "
 >
 <