--- a/layout/style/nsStyleTransformMatrix.cpp
+++ b/layout/style/nsStyleTransformMatrix.cpp
@@ -34,58 +34,50 @@ namespace nsStyleTransformMatrix {
 static double FlushToZero(double aVal)
 {
   if (-FLT_EPSILON < aVal && aVal < FLT_EPSILON)
     return 0.0f;
   else
     return aVal;
 }
 
-/* Helper function to fill in an nscoord with the specified nsCSSValue. */
-static nscoord CalcLength(const nsCSSValue &aValue,
-                          nsStyleContext* aContext,
-                          nsPresContext* aPresContext,
-                          bool &aCanStoreInRuleTree)
-{
-  if (aValue.GetUnit() == eCSSUnit_Pixel ||
-      aValue.GetUnit() == eCSSUnit_Number) {
-    // Handle this here (even though nsRuleNode::CalcLength handles it
-    // fine) so that callers are allowed to pass a null style context
-    // and pres context to SetToTransformFunction if they know (as
-    // nsStyleAnimation does) that all lengths within the transform
-    // function have already been computed to pixels and percents.
-    //
-    // Raw numbers are treated as being pixels.
-    return nsPresContext::CSSPixelsToAppUnits(aValue.GetFloatValue());
-  }
-  return nsRuleNode::CalcLength(aValue, aContext, aPresContext,
-                                aCanStoreInRuleTree);
-}
-
 static float
 ProcessTranslatePart(const nsCSSValue& aValue,
                      nsStyleContext* aContext,
                      nsPresContext* aPresContext,
                      bool& aCanStoreInRuleTree,
                      nscoord aSize, float aAppUnitsPerMatrixUnit)
 {
   nscoord offset = 0;
   float percent = 0.0f;
 
   if (aValue.GetUnit() == eCSSUnit_Percent) {
     percent = aValue.GetPercentValue();
+  } else if (aValue.GetUnit() == eCSSUnit_Pixel ||
+             aValue.GetUnit() == eCSSUnit_Number) {
+    // Handle this here (even though nsRuleNode::CalcLength handles it
+    // fine) so that callers are allowed to pass a null style context
+    // and pres context to SetToTransformFunction if they know (as
+    // nsStyleAnimation does) that all lengths within the transform
+    // function have already been computed to pixels and percents.
+    //
+    // Raw numbers are treated as being pixels.
+    //
+    // Don't convert to aValue to AppUnits here to avoid precision issues.
+    return aValue.GetFloatValue() *
+           (float(nsPresContext::AppUnitsPerCSSPixel()) / aAppUnitsPerMatrixUnit);
   } else if (aValue.IsCalcUnit()) {
     nsRuleNode::ComputedCalc result =
       nsRuleNode::SpecifiedCalcToComputedCalc(aValue, aContext, aPresContext,
                                               aCanStoreInRuleTree);
     percent = result.mPercent;
     offset = result.mLength;
   } else {
-    offset = CalcLength(aValue, aContext, aPresContext,
-                         aCanStoreInRuleTree);
+    offset = nsRuleNode::CalcLength(aValue, aContext, aPresContext,
+                                    aCanStoreInRuleTree);
   }
 
   return (percent * NSAppUnitsToFloatPixels(aSize, aAppUnitsPerMatrixUnit)) + 
          NSAppUnitsToFloatPixels(offset, aAppUnitsPerMatrixUnit);
 }
 
 /**
  * Helper functions to process all the transformation function types.