diff --git a/layout/base/nsPresContext.h b/layout/base/nsPresContext.h
index 0f5a96385d7b..063c769df69a 100644
--- a/layout/base/nsPresContext.h
+++ b/layout/base/nsPresContext.h
@@ -600,8 +600,8 @@ public:
                    AppUnitsToGfxUnits(aAppRect.height)); }
 
   nscoord TwipsToAppUnits(PRInt32 aTwips) const
-  { return NSToCoordRound(NS_TWIPS_TO_INCHES(aTwips) *
-                          mDeviceContext->AppUnitsPerInch()); }
+  { return NSCoordSaturatingMultiply(NS_TWIPS_TO_INCHES(aTwips),
+                                     mDeviceContext->AppUnitsPerInch()); }
 
   // Margin-specific version, since they often need TwipsToAppUnits
   nsMargin TwipsToAppUnits(const nsIntMargin &marginInTwips) const
diff --git a/layout/reftests/backgrounds/reftest.list b/layout/reftests/backgrounds/reftest.list
index 6c4375198045..a0c34c549a95 100644
--- a/layout/reftests/backgrounds/reftest.list
+++ b/layout/reftests/backgrounds/reftest.list
@@ -80,13 +80,13 @@
 != background-size-cover-each-box.html background-size-cover-bounding-box.html
 
 == background-size-monster-ch.html background-size-monster-ref.html
-random == background-size-monster-cm.html background-size-monster-ref.html
+== background-size-monster-cm.html background-size-monster-ref.html
 == background-size-monster-em.html background-size-monster-ref.html
 == background-size-monster-ex.html background-size-monster-ref.html
-random == background-size-monster-inches.html background-size-monster-ref.html
-random == background-size-monster-mm.html background-size-monster-ref.html
-random == background-size-monster-pc.html background-size-monster-ref.html
-random == background-size-monster-pt.html background-size-monster-ref.html
+== background-size-monster-inches.html background-size-monster-ref.html
+== background-size-monster-mm.html background-size-monster-ref.html
+== background-size-monster-pc.html background-size-monster-ref.html
+== background-size-monster-pt.html background-size-monster-ref.html
 == background-size-monster-px.html background-size-monster-ref.html
 == background-size-monster-rem.html background-size-monster-ref.html