Add support for multiple text decorations with same line positioning

Source/core/style/StyleRareInheritedData.h

Index: Source/core/style/StyleRareInheritedData.h
diff --git a/Source/core/style/StyleRareInheritedData.h b/Source/core/style/StyleRareInheritedData.h
index 0e04f4203f58260465264edd6dc1e98b0c7513d1..9f9f08501d4fd92cf4e208ae21401f466b208c81 100644
--- a/Source/core/style/StyleRareInheritedData.h
+++ b/Source/core/style/StyleRareInheritedData.h
@@ -133,7 +133,7 @@ public:
     unsigned m_textIndentType : 1; // TextIndentHanging
     // CSS Image Values Level 3
     unsigned m_imageRendering : 3; // EImageRendering
-    unsigned m_textUnderlinePosition : 1; // TextUnderlinePosition
+    unsigned m_hasSimpleUnderlinePosition : 1; // TextUnderlinePosition
     unsigned m_rubyPosition : 1; // RubyPosition
 
     // Though will-change is not itself an inherited property, the intent
@@ -156,6 +156,8 @@ public:
 
     Color tapHighlightColor;
 
+    Color simpleUnderlineColor;
+    Color simpleUnderlineVisitedColor;
     RefPtr<AppliedTextDecorationList> appliedTextDecorations;
     TabSize m_tabSize;