Bug 1881495 part 1: Add ShrinkWrap flag for grid items that are self-…

…aligned (not stretched) in MeasuringReflow(). r=dholbert

Bug 1350037 Part 3 [1] removed the code in ReflowInput that adds `ShrinkWrap`
flag self-aligned grid items, to prevent the table-caption from getting aligned
behavior, but it accidentally broke self-aligned behavior for other types of
frames that are grid items.

We actually already check if we need to add `ShrinkWrap` in grid item's final
reflow [2], but we were missing the same logic in `MeasuringReflow()`. This
patch adds that.

[1] https://hg.mozilla.org/mozilla-central/rev/6e8085865f74
[2] https://searchfox.org/mozilla-central/rev/202c48686136360a23b73a49b611a19e64f3e1b8/layout/generic/nsGridContainerFrame.cpp#7651,7657

Differential Revision: https://phabricator.services.mozilla.com/D203514

layout/generic/nsGridContainerFrame.cpp

@@ -5300,7 +5300,8 @@ static nscoord MeasuringReflow(nsIFrame* aChild,
                                const LogicalSize& aCBSize,
                                nscoord aIMinSizeClamp = NS_MAXSIZE,
                                nscoord aBMinSizeClamp = NS_MAXSIZE) {
-  nsContainerFrame* parent = aChild->GetParent();
+  MOZ_ASSERT(aChild->IsGridItem(), "aChild should be a grid item!");
+  auto* parent = static_cast<nsGridContainerFrame*>(aChild->GetParent());
   nsPresContext* pc = aChild->PresContext();
   Maybe<ReflowInput> dummyParentState;
   const ReflowInput* rs = aReflowInput;
@@ -5319,6 +5320,11 @@ static nscoord MeasuringReflow(nsIFrame* aChild,
 #endif
   auto wm = aChild->GetWritingMode();
   ComputeSizeFlags csFlags = ComputeSizeFlag::IsGridMeasuringReflow;
+  // Shrink-wrap grid items that will be aligned (rather than stretched) in
+  // their own inline axis.
+  if (!parent->GridItemShouldStretch(aChild, eLogicalAxisInline)) {
+    csFlags += ComputeSizeFlag::ShrinkWrap;
+  }
   if (aAvailableSize.ISize(wm) == INFINITE_ISIZE_COORD) {
     csFlags += ComputeSizeFlag::ShrinkWrap;
   }