Bug 1308110 - make tab-size animatable. r=cam

dom/animation/test/mozilla/file_discrete-animations.html

@@ -75,11 +75,6 @@ const gMozillaSpecificProperties = {
     from: "ignore",
     to: "stretch-to-fit"
   },
-  "-moz-tab-size": {
-    // https://drafts.csswg.org/css-text-3/#propdef-tab-size
-    from: "1",
-    to: "5"
-  },
   "-moz-text-size-adjust": {
     // https://drafts.csswg.org/css-size-adjust/#propdef-text-size-adjust
     from: "none",

layout/style/nsCSSPropList.h

@@ -3878,7 +3878,7 @@ CSS_PROP_TEXT(
     VARIANT_INHERIT | VARIANT_LNCALC,
     nullptr,
     offsetof(nsStyleText, mTabSize),
-    eStyleAnimType_Discrete)
+    eStyleAnimType_Coord)
 CSS_PROP_TABLE(
     table-layout,
     table_layout,

layout/style/test/test_transitions_per_property.html

@@ -248,6 +248,8 @@ var supported_properties = {
     // test_length_percent_calc_transition.
     "stroke-width": [ test_length_transition_svg, test_percent_transition,
                       test_length_clamped_svg, test_percent_clamped ],
+    "-moz-tab-size": [ test_float_zeroToOne_transition,
+                       test_float_aboveOne_transition, test_length_clamped ],
     "text-decoration": [ test_color_shorthand_transition,
                          test_true_currentcolor_shorthand_transition ],
     "text-decoration-color": [ test_color_transition,