Bug 1500609 part 1 - Add a nsFlexContainerFrame method to remove cached data that depend on flex items' intrinsic isize (idempotent patch). r=dholbert

layout/generic/nsFlexContainerFrame.cpp

@@ -1818,6 +1818,12 @@ public:
 NS_DECLARE_FRAME_PROPERTY_DELETABLE(CachedFlexMeasuringReflow,
                                     CachedMeasuringReflowResult);
 
+void
+nsFlexContainerFrame::MarkCachedFlexMeasurementsDirty(nsIFrame* aItemFrame)
+{
+  aItemFrame->DeleteProperty(CachedFlexMeasuringReflow());
+}
+
 const CachedMeasuringReflowResult&
 nsFlexContainerFrame::MeasureAscentAndBSizeForFlexItem(
   FlexItem& aItem,

layout/generic/nsFlexContainerFrame.h

@@ -232,6 +232,11 @@ public:
   static bool IsUsedFlexBasisContent(const nsStyleCoord* aFlexBasis,
                                      const nsStyleCoord* aMainSize);
 
+  /**
+   * Callback for nsFrame::MarkIntrinsicISizesDirty() on a flex item.
+   */
+  static void MarkCachedFlexMeasurementsDirty(nsIFrame* aItemFrame);
+
 protected:
   // Protected constructor & destructor
   explicit nsFlexContainerFrame(ComputedStyle* aStyle)

layout/generic/nsFrame.cpp

@@ -5220,7 +5220,7 @@ nsFrame::MarkIntrinsicISizesDirty()
   // (which likely depended on our now-stale intrinsic isize).
   auto* parentFrame = GetParent();
   if (parentFrame && parentFrame->IsFlexContainerFrame()) {
-    DeleteProperty(CachedFlexMeasuringReflow());
+    nsFlexContainerFrame::MarkCachedFlexMeasurementsDirty(this);
   }
 
   if (GetStateBits() & NS_FRAME_FONT_INFLATION_FLOW_ROOT) {