diff --git a/layout/base/nsLayoutUtils.cpp b/layout/base/nsLayoutUtils.cpp
index 1eeb495d9e9..c334406aab5 100644
--- a/layout/base/nsLayoutUtils.cpp
+++ b/layout/base/nsLayoutUtils.cpp
@@ -1243,11 +1243,8 @@ static PRBool GetAbsoluteCoord(const nsStyleCoord& aStyle,
     return PR_TRUE;
   }
   if (eStyleUnit_Chars == unit) {
-    SetFontFromStyle(aRenderingContext, aFrame->GetStyleContext());
-    nscoord fontWidth;
-    aRenderingContext->SetTextRunRTL(PR_FALSE);
-    aRenderingContext->GetWidth('M', fontWidth);
-    aResult = aStyle.GetIntValue() * fontWidth;
+    aResult = nsLayoutUtils::CharsToCoord(aStyle, aRenderingContext,
+                                          aFrame->GetStyleContext());
     return PR_TRUE;
   }
   return PR_FALSE;
@@ -2154,3 +2151,27 @@ nsLayoutUtils::DrawImage(nsIRenderingContext* aRenderingContext,
    */
 #endif
 }
+
+void
+nsLayoutUtils::SetFontFromStyle(nsIRenderingContext* aRC, nsStyleContext* aSC) 
+{
+  const nsStyleFont* font = aSC->GetStyleFont();
+  const nsStyleVisibility* visibility = aSC->GetStyleVisibility();
+
+  aRC->SetFont(font->mFont, visibility->mLangGroup);
+}
+
+nscoord
+nsLayoutUtils::CharsToCoord(const nsStyleCoord& aStyle,
+                            nsIRenderingContext* aRenderingContext,
+                            nsStyleContext* aStyleContext)
+{
+  NS_ASSERTION(aStyle.GetUnit() == eStyleUnit_Chars,
+               "Shouldn't have called this");
+
+  SetFontFromStyle(aRenderingContext, aStyleContext);
+  nscoord fontWidth;
+  aRenderingContext->SetTextRunRTL(PR_FALSE);
+  aRenderingContext->GetWidth('M', fontWidth);
+  return aStyle.GetIntValue() * fontWidth;
+}
diff --git a/layout/base/nsLayoutUtils.h b/layout/base/nsLayoutUtils.h
index ac8d24e228e..18e6fd415d0 100644
--- a/layout/base/nsLayoutUtils.h
+++ b/layout/base/nsLayoutUtils.h
@@ -647,6 +647,22 @@ public:
                             const nsRect& aDestRect,
                             const nsRect& aDirtyRect,
                             const nsRect* aSourceRect = nsnull);
+
+  /**
+   * Set the font on aRC based on the style in aSC
+   */
+  static void SetFontFromStyle(nsIRenderingContext* aRC, nsStyleContext* aSC);
+
+  /**
+   * Convert an eStyleUnit_Chars nsStyleCoord to an nscoord.
+   *
+   * @param aStyle the style coord
+   * @param aRenderingContext the rendering context to use for font measurement
+   * @param aStyleContext the style context to use for font infomation
+   */
+  static nscoord CharsToCoord(const nsStyleCoord& aStyle,
+                              nsIRenderingContext* aRenderingContext,
+                              nsStyleContext* aStyleContext);
 };
 
 #endif // nsLayoutUtils_h__
diff --git a/layout/generic/nsBRFrame.cpp b/layout/generic/nsBRFrame.cpp
index d551df7aef8..13d501553d1 100644
--- a/layout/generic/nsBRFrame.cpp
+++ b/layout/generic/nsBRFrame.cpp
@@ -46,7 +46,7 @@
 #include "nsGkAtoms.h"
 #include "nsIFontMetrics.h"
 #include "nsIRenderingContext.h"
-#include "nsTextTransformer.h"
+#include "nsLayoutUtils.h"
 
 #ifdef ACCESSIBILITY
 #include "nsIServiceManager.h"
@@ -144,7 +144,7 @@ BRFrame::Reflow(nsPresContext* aPresContext,
       // We also do this in strict mode because BR should act like a
       // normal inline frame.  That line-height is used is important
       // here for cases where the line-height is less that 1.
-      SetFontFromStyle(aReflowState.rendContext, mStyleContext);
+      nsLayoutUtils::SetFontFromStyle(aReflowState.rendContext, mStyleContext);
       nsCOMPtr<nsIFontMetrics> fm;
       aReflowState.rendContext->GetFontMetrics(*getter_AddRefs(fm));
       if (fm) {
diff --git a/layout/generic/nsFrame.cpp b/layout/generic/nsFrame.cpp
index 49c87326c00..a940a1e50a7 100644
--- a/layout/generic/nsFrame.cpp
+++ b/layout/generic/nsFrame.cpp
@@ -437,15 +437,6 @@ nsresult NS_NewSelectionImageService(nsISelectionImageService** aResult)
 
 //end selection service
 
-// a handy utility to set font
-void SetFontFromStyle(nsIRenderingContext* aRC, nsStyleContext* aSC) 
-{
-  const nsStyleFont* font = aSC->GetStyleFont();
-  const nsStyleVisibility* visibility = aSC->GetStyleVisibility();
-
-  aRC->SetFont(font->mFont, visibility->mLangGroup);
-}
-
 void
 nsWeakFrame::Init(nsIFrame* aFrame)
 {
@@ -3059,11 +3050,8 @@ AddCoord(const nsStyleCoord& aStyle,
       *aPercent += aStyle.GetPercentValue();
       break;
     case eStyleUnit_Chars: {
-      SetFontFromStyle(aRenderingContext, aFrame->GetStyleContext());
-      nscoord fontWidth;
-      aRenderingContext->SetTextRunRTL(PR_FALSE);
-      aRenderingContext->GetWidth('M', fontWidth);
-      *aCoord += aStyle.GetIntValue() * fontWidth;
+      *aCoord += nsLayoutUtils::CharsToCoord(aStyle, aRenderingContext,
+                                             aFrame->GetStyleContext());
       break;
     }
     default:
diff --git a/layout/generic/nsFrame.h b/layout/generic/nsFrame.h
index 4024b24b24f..28b7a8bd69b 100644
--- a/layout/generic/nsFrame.h
+++ b/layout/generic/nsFrame.h
@@ -113,10 +113,6 @@
 #define NS_FRAME_TRACE_REFLOW_OUT(_method, _status)
 #endif
 
-// handy utilities
-// XXXldb Move to nsLayoutUtils!
-void SetFontFromStyle(nsIRenderingContext* aRC, nsStyleContext* aSC);
-
 //----------------------------------------------------------------------
 
 struct nsBoxLayoutMetrics;
diff --git a/layout/generic/nsImageFrame.cpp b/layout/generic/nsImageFrame.cpp
index 38c6d66c38e..4476d8db940 100644
--- a/layout/generic/nsImageFrame.cpp
+++ b/layout/generic/nsImageFrame.cpp
@@ -941,7 +941,7 @@ nsImageFrame::DisplayAltText(nsPresContext*      aPresContext,
 {
   // Set font and color
   aRenderingContext.SetColor(GetStyleColor()->mColor);
-  SetFontFromStyle(&aRenderingContext, mStyleContext);
+  nsLayoutUtils::SetFontFromStyle(&aRenderingContext, mStyleContext);
 
   // Format the text to display within the formatting rect
   nsIFontMetrics* fm;
diff --git a/layout/generic/nsInlineFrame.cpp b/layout/generic/nsInlineFrame.cpp
index ef6b943b4dc..023ab76fa68 100644
--- a/layout/generic/nsInlineFrame.cpp
+++ b/layout/generic/nsInlineFrame.cpp
@@ -568,7 +568,7 @@ nsInlineFrame::ReflowFrames(nsPresContext* aPresContext,
                             : aReflowState.mComputedBorderPadding.left;
     }
 
-    SetFontFromStyle(aReflowState.rendContext, mStyleContext);
+    nsLayoutUtils::SetFontFromStyle(aReflowState.rendContext, mStyleContext);
     nsCOMPtr<nsIFontMetrics> fm;
     aReflowState.rendContext->GetFontMetrics(*getter_AddRefs(fm));
 
diff --git a/layout/generic/nsLineLayout.cpp b/layout/generic/nsLineLayout.cpp
index 84fec164bc9..bda7fd5248a 100644
--- a/layout/generic/nsLineLayout.cpp
+++ b/layout/generic/nsLineLayout.cpp
@@ -1615,7 +1615,7 @@ nsLineLayout::VerticalAlignFrames(PerSpanData* psd)
   // Get the parent frame's font for all of the frames in this span
   nsStyleContext* styleContext = spanFrame->GetStyleContext();
   nsIRenderingContext* rc = mBlockReflowState->rendContext;
-  SetFontFromStyle(mBlockReflowState->rendContext, styleContext);
+  nsLayoutUtils::SetFontFromStyle(mBlockReflowState->rendContext, styleContext);
   nsCOMPtr<nsIFontMetrics> fm;
   rc->GetFontMetrics(*getter_AddRefs(fm));
 
diff --git a/layout/generic/nsTextFrame.cpp b/layout/generic/nsTextFrame.cpp
index b6fae47ef99..1921bda3d79 100644
--- a/layout/generic/nsTextFrame.cpp
+++ b/layout/generic/nsTextFrame.cpp
@@ -893,7 +893,8 @@ nsTextStyle::nsTextStyle(nsPresContext* aPresContext,
   PRUint8 originalDecorations = plainFont->decorations;
   plainFont->decorations = NS_FONT_DECORATION_NONE;
   mAveCharWidth = 0;
-  SetFontFromStyle(&aRenderingContext, sc); // some users of the struct expect this state
+  // Set the font: some users of the struct expect this state
+  nsLayoutUtils::SetFontFromStyle(&aRenderingContext, sc);
   aRenderingContext.GetFontMetrics(mNormalFont);
   mNormalFont->GetSpaceWidth(mSpaceWidth);
   mNormalFont->GetAveCharWidth(mAveCharWidth);
@@ -2140,7 +2141,7 @@ nsTextFrame::FillClusterBuffer(nsPresContext *aPresContext, const PRUnichar *aTe
     NS_ENSURE_SUCCESS(rv, rv);
 
     // Find the font metrics for this text
-    SetFontFromStyle(acx, mStyleContext);
+    nsLayoutUtils::SetFontFromStyle(acx, mStyleContext);
 
     acx->GetHints(clusterHint);
     clusterHint &= NS_RENDERING_HINT_TEXT_CLUSTERS;
@@ -4131,7 +4132,7 @@ nsTextFrame::GetPositionHelper(const nsPoint&  aPoint,
       }
 
       // Find the font metrics for this text
-      SetFontFromStyle(rendContext, mStyleContext);
+      nsLayoutUtils::SetFontFromStyle(rendContext, mStyleContext);
 
       // Get the renderable form of the text
       nsTextTransformer tx(PresContext());
@@ -6173,7 +6174,7 @@ nsTextFrame::Reflow(nsPresContext*          aPresContext,
 
 #ifdef MOZ_MATHML
     if (calcMathMLMetrics) {
-      SetFontFromStyle(aReflowState.rendContext, mStyleContext);
+      nsLayoutUtils::SetFontFromStyle(aReflowState.rendContext, mStyleContext);
       nsBoundingMetrics bm;
       rv = aReflowState.rendContext->GetBoundingMetrics(textBuffer.mBuffer, textLength, bm);
       if (NS_SUCCEEDED(rv))
@@ -6277,7 +6278,7 @@ nsTextFrame::TrimTrailingWhiteSpace(nsPresContext* aPresContext,
         if (XP_IS_SPACE(ch)) {
           // Get font metrics for a space so we can adjust the width by the
           // right amount.
-          SetFontFromStyle(&aRC, mStyleContext);
+          nsLayoutUtils::SetFontFromStyle(&aRC, mStyleContext);
 
           aRC.GetWidth(' ', dw);
           // NOTE: Trailing whitespace includes word and letter spacing!
diff --git a/layout/reftests/bugs/371043-1-ref.html b/layout/reftests/bugs/371043-1-ref.html
new file mode 100644
index 00000000000..022d34aa183
--- /dev/null
+++ b/layout/reftests/bugs/371043-1-ref.html
@@ -0,0 +1,9 @@
+<!DOCTYPE html>
+<body>
+  <div id="source" style="font-size: 10px; -moz-column-gap: 2ch">
+    <span id="test"
+          style="background: green; color: green; display: inline-block;
+                 height: 30px; padding: 0 2px">MM
+    </span>
+  </div>
+</body>
diff --git a/layout/reftests/bugs/371043-1.html b/layout/reftests/bugs/371043-1.html
new file mode 100644
index 00000000000..735e7d52746
--- /dev/null
+++ b/layout/reftests/bugs/371043-1.html
@@ -0,0 +1,14 @@
+<!DOCTYPE html>
+<body>
+  <div id="source" style="font-size: 10px; -moz-column-gap: 2ch">
+    <span id="test"
+          style="background: green; display: inline-block; height: 30px;
+                 padding: 0 2px">
+    </span>
+    <script>
+      document.getElementById("test").style.width =
+        document.defaultView.getComputedStyle(document.getElementById("source"),
+                                              "").MozColumnGap;
+    </script>
+  </div>
+</body>
diff --git a/layout/reftests/bugs/reftest.list b/layout/reftests/bugs/reftest.list
index dd5b50bb5a3..bdb4b02590c 100644
--- a/layout/reftests/bugs/reftest.list
+++ b/layout/reftests/bugs/reftest.list
@@ -210,6 +210,7 @@ fails == 368504-1.html 368504-1-ref.html # bug 368504
 == 370629-2.html 370629-2-ref.html
 == 370692-1.xhtml 370692-1-ref.xhtml
 == 371041-1.html 371041-1-ref.html
+== 371043-1.html 371043-1-ref.html
 == 371925-1a.html 371925-1-ref.html
 == 371925-1b.html 371925-1-ref.html
 == 372553-1.html 372553-1-ref.html
diff --git a/layout/style/nsComputedDOMStyle.cpp b/layout/style/nsComputedDOMStyle.cpp
index a5a61e323e6..eea9be6e874 100644
--- a/layout/style/nsComputedDOMStyle.cpp
+++ b/layout/style/nsComputedDOMStyle.cpp
@@ -68,6 +68,8 @@
 #include "nsStyleSet.h"
 #include "imgIRequest.h"
 #include "nsInspectorCSSUtils.h"
+#include "nsLayoutUtils.h"
+#include "nsFrameManager.h"
 
 #if defined(DEBUG_bzbarsky) || defined(DEBUG_caillon)
 #define DEBUG_ComputedDOMStyle
@@ -2747,11 +2749,24 @@ nsComputedDOMStyle::SetValueToCoord(nsROCSSPrimitiveValue* aValue,
                                                   aTable));
       break;
       
-    case eStyleUnit_Chars:
-      // XXX we need a frame and a rendering context to calculate this, bug 281972, bug 282126.
-      aValue->SetAppUnits(0);
+    case eStyleUnit_Chars: {
+      // Get a rendering context
+      nsCOMPtr<nsIRenderingContext> cx;
+      nsIFrame* frame = mPresShell->FrameManager()->GetRootFrame();
+      if (frame) {
+        mPresShell->CreateRenderingContext(frame, getter_AddRefs(cx));
+      }
+      if (cx) {
+        nscoord val =
+          nsLayoutUtils::CharsToCoord(aCoord, cx, mStyleContextHolder);
+        aValue->SetAppUnits(PR_MAX(aMinAppUnits, val));
+      } else {
+        // Oh, well.  Give up.
+        aValue->SetAppUnits(0);
+      }
       break;
-      
+    }
+
     case eStyleUnit_Null:
       aValue->SetIdent(nsGkAtoms::none);
       break;