--- a/layout/style/StyleAnimationValue.cpp
+++ b/layout/style/StyleAnimationValue.cpp
@@ -4134,24 +4134,16 @@ StyleAnimationValue::ExtractComputedValu
       aComputedValue.SetAndAdoptCSSValuePairValue(pair.forget(),
                                                   eUnit_CSSValuePair);
       return true;
     }
     case eStyleAnimType_nscoord:
       aComputedValue.SetCoordValue(*static_cast<const nscoord*>(
         StyleDataAtOffset(styleStruct, ssOffset)));
       return true;
-    case eStyleAnimType_EnumU8:
-      aComputedValue.SetIntValue(*static_cast<const uint8_t*>(
-        StyleDataAtOffset(styleStruct, ssOffset)), eUnit_Enumerated);
-      if (aProperty == eCSSProperty_visibility) {
-        aComputedValue.SetIntValue(aComputedValue.GetIntValue(),
-                                   eUnit_Visibility);
-      }
-      return true;
     case eStyleAnimType_float:
       aComputedValue.SetFloatValue(*static_cast<const float*>(
         StyleDataAtOffset(styleStruct, ssOffset)));
       if (aProperty == eCSSProperty_font_size_adjust &&
           aComputedValue.GetFloatValue() == -1.0f) {
         // In nsStyleFont, we set mFont.sizeAdjust to -1.0 to represent
         // font-size-adjust: none.  Here, we have to treat this as a keyword
         // instead of a float value, to make sure we don't end up doing

--- a/layout/style/nsCSSProps.h
+++ b/layout/style/nsCSSProps.h
@@ -303,22 +303,16 @@ enum nsStyleAnimType {
   eStyleAnimType_Corner_TopLeft,
   eStyleAnimType_Corner_TopRight,
   eStyleAnimType_Corner_BottomRight,
   eStyleAnimType_Corner_BottomLeft,
 
   // nscoord values
   eStyleAnimType_nscoord,
 
-  // enumerated values (stored in a uint8_t)
-  // In order for a property to use this unit, _all_ of its enumerated values
-  // must be listed in its keyword table, so that any enumerated value can be
-  // converted into a string via a nsCSSValue of type eCSSUnit_Enumerated.
-  eStyleAnimType_EnumU8,
-
   // float values
   eStyleAnimType_float,
 
   // nscolor values
   eStyleAnimType_Color,
 
   // nsStyleSVGPaint values
   eStyleAnimType_PaintServer,