This is a better fix for the build bustage caused by the checkin for bug 294086. Thanks to Peter Annema for explaining the issue (don't assign to rvalues) and this fix.

layout/base/nsLayoutUtils.cpp

@@ -1735,7 +1735,7 @@ IsAutoHeight(const nsStyleCoord &aCoord, nscoord aCBHeight)
 /* static */ nsSize
 nsLayoutUtils::ComputeSizeWithIntrinsicDimensions(
                    nsIRenderingContext* aRenderingContext, nsIFrame* aFrame,
-                   nsIFrame::IntrinsicSize aIntrinsicSize,
+                   const nsIFrame::IntrinsicSize& aIntrinsicSize,
                    nsSize aIntrinsicRatio, nsSize aCBSize,
                    nsSize aMargin, nsSize aBorder, nsSize aPadding)
 {

layout/base/nsLayoutUtils.h

@@ -626,7 +626,7 @@ public:
    */
   static nsSize ComputeSizeWithIntrinsicDimensions(
                     nsIRenderingContext* aRenderingContext, nsIFrame* aFrame,
-                    nsIFrame::IntrinsicSize aIntrinsicSize,
+                    const nsIFrame::IntrinsicSize& aIntrinsicSize,
                     nsSize aIntrinsicRatio, nsSize aCBSize,
                     nsSize aMargin, nsSize aBorder, nsSize aPadding);