Bug 1255393 part 3 - [css-grid] Update 'auto' min track sizing for span=1 to the latest Grid spec. r=dholbert

Now it returns the min/max-content contribution for intrinsic sizing.
Otherwise, i.e. during Reflow, return the min-size contribution.
(Previously, it always returned the min-size contribution.)
https://drafts.csswg.org/css-grid/#algo-content

layout/generic/nsGridContainerFrame.cpp

@@ -3781,7 +3781,15 @@ nsGridContainerFrame::Tracks::ResolveIntrinsicSizeStep1(
   WritingMode wm = aState.mWM;
   nsRenderingContext* rc = &aState.mRenderingContext;
   if (sz.mState & TrackSize::eAutoMinSizing) {
-    nscoord s = MinSize(aGridItem, aState, rc, wm, mAxis);
+    nscoord s;
+    if (aConstraint == SizingConstraint::eMinContent) {
+      s = MinContentContribution(aGridItem, aState, rc, wm, mAxis);
+    } else if (aConstraint == SizingConstraint::eMaxContent) {
+      s = MaxContentContribution(aGridItem, aState, rc, wm, mAxis);
+    } else {
+      MOZ_ASSERT(aConstraint == SizingConstraint::eNoConstraint);
+      s = MinSize(aGridItem, aState, rc, wm, mAxis);
+    }
     sz.mBase = std::max(sz.mBase, s);
   } else if ((sz.mState & TrackSize::eMinContentMinSizing) ||
              (aConstraint == SizingConstraint::eMinContent &&