Reset the stretchy flags of underscript/overscript frames when their geometry is expected to be like subscript/superscirpt frames

layout/mathml/base/src/nsMathMLmoverFrame.cpp

@@ -208,6 +208,12 @@ XXX The winner is the outermost in conflicting settings like these:
        NS_MATHML_DISPLAYSTYLE | compress);
   }
 
+  // disable the strecth-all flag if we are going to act like an overscript
+  if ( NS_MATHML_IS_MOVABLELIMITS(mPresentationData.flags) &&
+      !NS_MATHML_IS_DISPLAYSTYLE(mPresentationData.flags)) {
+    mEmbellishData.flags &= ~NS_MATHML_STRETCH_ALL_CHILDREN_HORIZONTALLY;
+  }
+
   return rv;
 }
 

layout/mathml/base/src/nsMathMLmunderFrame.cpp

@@ -202,6 +202,12 @@ XXX The winner is the outermost setting in conflicting settings like these:
        NS_MATHML_DISPLAYSTYLE | NS_MATHML_COMPRESSED);
   }
 
+  // disable the strecth-all flag if we are going to act like an subscript
+  if ( NS_MATHML_IS_MOVABLELIMITS(mPresentationData.flags) &&
+      !NS_MATHML_IS_DISPLAYSTYLE(mPresentationData.flags)) {
+    mEmbellishData.flags &= ~NS_MATHML_STRETCH_ALL_CHILDREN_HORIZONTALLY;
+  }
+
   return rv;
 }
 

layout/mathml/base/src/nsMathMLmunderoverFrame.cpp

@@ -254,6 +254,12 @@ nsMathMLmunderoverFrame::SetInitialChildList(nsIPresContext* aPresContext,
        NS_MATHML_DISPLAYSTYLE | NS_MATHML_COMPRESSED);
   }
 
+  // disable the strecth-all flag if we are going to act like an subscript-superscript pair
+  if ( NS_MATHML_IS_MOVABLELIMITS(mPresentationData.flags) &&
+      !NS_MATHML_IS_DISPLAYSTYLE(mPresentationData.flags)) {
+    mEmbellishData.flags &= ~NS_MATHML_STRETCH_ALL_CHILDREN_HORIZONTALLY;
+  }
+
   return rv;
 }