--- a/layout/base/nsLayoutUtils.cpp
+++ b/layout/base/nsLayoutUtils.cpp
@@ -4163,48 +4163,65 @@ nsLayoutUtils::ComputeObjectDestRect(con
     }
   }
   return nsRect(imageTopLeftPt, concreteObjectSize);
 }
 
 already_AddRefed<nsFontMetrics>
 nsLayoutUtils::GetFontMetricsForFrame(const nsIFrame* aFrame, float aInflation)
 {
-  return GetFontMetricsForStyleContext(aFrame->StyleContext(), aInflation);
+  nsStyleContext* styleContext = aFrame->StyleContext();
+  uint8_t variantWidth = NS_FONT_VARIANT_WIDTH_NORMAL;
+  if (styleContext->IsTextCombined()) {
+    MOZ_ASSERT(aFrame->GetType() == nsGkAtoms::textFrame);
+    auto textFrame = static_cast<const nsTextFrame*>(aFrame);
+    auto clusters = textFrame->CountGraphemeClusters();
+    if (clusters == 2) {
+      variantWidth = NS_FONT_VARIANT_WIDTH_HALF;
+    } else if (clusters == 3) {
+      variantWidth = NS_FONT_VARIANT_WIDTH_THIRD;
+    } else if (clusters == 4) {
+      variantWidth = NS_FONT_VARIANT_WIDTH_QUARTER;
+    }
+  }
+  return GetFontMetricsForStyleContext(styleContext, aInflation, variantWidth);
 }
 
 already_AddRefed<nsFontMetrics>
 nsLayoutUtils::GetFontMetricsForStyleContext(nsStyleContext* aStyleContext,
-                                             float aInflation)
+                                             float aInflation,
+                                             uint8_t aVariantWidth)
 {
   nsPresContext* pc = aStyleContext->PresContext();
 
   WritingMode wm(aStyleContext);
   const nsStyleFont* styleFont = aStyleContext->StyleFont();
   nsFontMetrics::Params params;
   params.language = styleFont->mLanguage;
   params.explicitLanguage = styleFont->mExplicitLanguage;
   params.orientation =
     wm.IsVertical() && !wm.IsSideways() ? gfxFont::eVertical
                                         : gfxFont::eHorizontal;
   // pass the user font set object into the device context to
   // pass along to CreateFontGroup
   params.userFontSet = pc->GetUserFontSet();
   params.textPerf = pc->GetTextPerfMetrics();
 
-  // When aInflation is 1.0, avoid making a local copy of the nsFont.
+  // When aInflation is 1.0 and we don't require width variant, avoid
+  // making a local copy of the nsFont.
   // This also avoids running font.size through floats when it is large,
   // which would be lossy.  Fortunately, in such cases, aInflation is
   // guaranteed to be 1.0f.
-  if (aInflation == 1.0f) {
+  if (aInflation == 1.0f && aVariantWidth == NS_FONT_VARIANT_WIDTH_NORMAL) {
     return pc->DeviceContext()->GetMetricsFor(styleFont->mFont, params);
   }
 
   nsFont font = styleFont->mFont;
   font.size = NSToCoordRound(font.size * aInflation);
+  font.variantWidth = aVariantWidth;
   return pc->DeviceContext()->GetMetricsFor(font, params);
 }
 
 nsIFrame*
 nsLayoutUtils::FindChildContainingDescendant(nsIFrame* aParent, nsIFrame* aDescendantFrame)
 {
   nsIFrame* result = aDescendantFrame;
 

--- a/layout/base/nsLayoutUtils.h
+++ b/layout/base/nsLayoutUtils.h
@@ -1250,17 +1250,18 @@ public:
   }
 
   /**
    * Get the font metrics corresponding to the given style data.
    * @param aStyleContext the style data
    * @param aSizeInflation number to multiply font size by
    */
   static already_AddRefed<nsFontMetrics> GetFontMetricsForStyleContext(
-      nsStyleContext* aStyleContext, float aSizeInflation = 1.0f);
+      nsStyleContext* aStyleContext, float aSizeInflation = 1.0f,
+      uint8_t aVariantWidth = NS_FONT_VARIANT_WIDTH_NORMAL);
 
   /**
    * Get the font metrics of emphasis marks corresponding to the given
    * style data. The result is same as GetFontMetricsForStyleContext
    * except that the font size is scaled down to 50%.
    * @param aStyleContext the style data
    * @param aInflation number to multiple font size by
    */