--- a/layout/generic/nsFlexContainerFrame.cpp
+++ b/layout/generic/nsFlexContainerFrame.cpp
@@ -253,21 +253,20 @@ private:
  * Represents a flex item.
  * Includes the various pieces of input that the Flexbox Layout Algorithm uses
  * to resolve a flexible width.
  */
 class nsFlexContainerFrame::FlexItem : public LinkedListElement<FlexItem>
 {
 public:
   // Normal constructor:
-  FlexItem(nsIFrame* aChildFrame,
+  FlexItem(nsHTMLReflowState& aFlexItemReflowState,
            float aFlexGrow, float aFlexShrink, nscoord aMainBaseSize,
            nscoord aMainMinSize, nscoord aMainMaxSize,
            nscoord aCrossMinSize, nscoord aCrossMaxSize,
-           nsMargin aMargin, nsMargin aBorderPadding,
            const FlexboxAxisTracker& aAxisTracker);
 
   // Simplified constructor, to be used only for generating "struts":
   FlexItem(nsIFrame* aChildFrame, nscoord aCrossSize);
 
   // Accessors
   nsIFrame* Frame() const          { return mFrame; }
   nscoord GetFlexBaseSize() const  { return mFlexBaseSize; }
@@ -1013,22 +1012,20 @@ nsFlexContainerFrame::GenerateFlexItemFo
       mainMaxSize = std::max(mainMaxSize, widgetMainMinSize);
 
       crossMinSize = std::max(crossMinSize, widgetCrossMinSize);
       crossMaxSize = std::max(crossMaxSize, widgetCrossMinSize);
     }
   }
 
   // Construct the flex item!
-  FlexItem* item = new FlexItem(aChildFrame,
+  FlexItem* item = new FlexItem(childRS,
                                 flexGrow, flexShrink, flexBaseSize,
                                 mainMinSize, mainMaxSize,
                                 crossMinSize, crossMaxSize,
-                                childRS.ComputedPhysicalMargin(),
-                                childRS.ComputedPhysicalBorderPadding(),
                                 aAxisTracker);
 
   // If we're inflexible, we can just freeze to our hypothetical main-size
   // up-front. Similarly, if we're a fixed-size widget, we only have one
   // valid size, so we freeze to keep ourselves from flexing.
   if (isFixedSizeWidget || (flexGrow == 0.0f && flexShrink == 0.0f)) {
     item->Freeze();
   }
@@ -1142,57 +1139,57 @@ nsFlexContainerFrame::
   }
   if (isMainMinSizeAuto) {
     aFlexItem.UpdateMainMinSize(childDesiredHeight);
   }
 
   aFlexItem.SetHadMeasuringReflow();
 }
 
-FlexItem::FlexItem(nsIFrame* aChildFrame,
+FlexItem::FlexItem(nsHTMLReflowState& aFlexItemReflowState,
                    float aFlexGrow, float aFlexShrink, nscoord aFlexBaseSize,
                    nscoord aMainMinSize,  nscoord aMainMaxSize,
                    nscoord aCrossMinSize, nscoord aCrossMaxSize,
-                   nsMargin aMargin, nsMargin aBorderPadding,
                    const FlexboxAxisTracker& aAxisTracker)
-  : mFrame(aChildFrame),
+  : mFrame(aFlexItemReflowState.frame),
     mFlexGrow(aFlexGrow),
     mFlexShrink(aFlexShrink),
-    mBorderPadding(aBorderPadding),
-    mMargin(aMargin),
+    mBorderPadding(aFlexItemReflowState.ComputedPhysicalBorderPadding()),
+    mMargin(aFlexItemReflowState.ComputedPhysicalMargin()),
     mMainMinSize(aMainMinSize),
     mMainMaxSize(aMainMaxSize),
     mCrossMinSize(aCrossMinSize),
     mCrossMaxSize(aCrossMaxSize),
     mMainPosn(0),
     mCrossSize(0),
     mCrossPosn(0),
     mAscent(0),
     mShareOfWeightSoFar(0.0f),
     mIsFrozen(false),
     mHadMinViolation(false),
     mHadMaxViolation(false),
     mHadMeasuringReflow(false),
     mIsStretched(false),
     mIsStrut(false),
-    mAlignSelf(aChildFrame->StylePosition()->mAlignSelf)
+    mAlignSelf(aFlexItemReflowState.mStylePosition->mAlignSelf)
 {
   MOZ_ASSERT(mFrame, "expecting a non-null child frame");
   MOZ_ASSERT(mFrame->GetType() != nsGkAtoms::placeholderFrame,
              "placeholder frames should not be treated as flex items");
   MOZ_ASSERT(!(mFrame->GetStateBits() & NS_FRAME_OUT_OF_FLOW),
              "out-of-flow frames should not be treated as flex items");
 
   SetFlexBaseSizeAndMainSize(aFlexBaseSize);
 
   // Assert that any "auto" margin components are set to 0.
   // (We'll resolve them later; until then, we want to treat them as 0-sized.)
 #ifdef DEBUG
   {
-    const nsStyleSides& styleMargin = mFrame->StyleMargin()->mMargin;
+    const nsStyleSides& styleMargin =
+      aFlexItemReflowState.mStyleMargin->mMargin;
     NS_FOR_CSS_SIDES(side) {
       if (styleMargin.GetUnit(side) == eStyleUnit_Auto) {
         MOZ_ASSERT(GetMarginComponentForSide(side) == 0,
                    "Someone else tried to resolve our auto margin");
       }
     }
   }
 #endif // DEBUG