--- a/layout/generic/nsFlexContainerFrame.cpp
+++ b/layout/generic/nsFlexContainerFrame.cpp
@@ -289,26 +289,16 @@ public:
   FlexboxAxisTracker(const nsFlexContainerFrame* aFlexContainer,
                      const WritingMode& aWM,
                      AxisTrackerFlags aFlags = eNoFlags);
 
   // Accessors:
   // XXXdholbert [BEGIN DEPRECATED]
   AxisOrientationType GetMainAxis() const  { return mMainAxis;  }
   AxisOrientationType GetCrossAxis() const { return mCrossAxis; }
-
-  bool IsMainAxisHorizontal() const {
-    // If we're row-oriented, and our writing mode is NOT vertical,
-    // or we're column-oriented and our writing mode IS vertical,
-    // then our main axis is horizontal. This handles all cases:
-    return mIsRowOriented != mWM.IsVertical();
-  }
-  bool IsCrossAxisHorizontal() const {
-    return !IsMainAxisHorizontal();
-  }
   // XXXdholbert [END DEPRECATED]
 
   // Returns the flex container's writing mode.
   WritingMode GetWritingMode() const { return mWM; }
 
   // Returns true if our main axis is in the reverse direction of our
   // writing mode's corresponding axis. (From 'flex-direction: *-reverse')
   bool IsMainAxisReversed() const {
@@ -407,16 +397,25 @@ public:
   }
 
 private:
   // Delete copy-constructor & reassignment operator, to prevent accidental
   // (unnecessary) copying.
   FlexboxAxisTracker(const FlexboxAxisTracker&) = delete;
   FlexboxAxisTracker& operator=(const FlexboxAxisTracker&) = delete;
 
+  // Private because callers shouldn't need to care about physical axes
+  // (but we do internally, to provide one API).
+  bool IsMainAxisHorizontal() const {
+    // If we're row-oriented, and our writing mode is NOT vertical,
+    // or we're column-oriented and our writing mode IS vertical,
+    // then our main axis is horizontal. This handles all cases:
+    return mIsRowOriented != mWM.IsVertical();
+  }
+
   // Helpers for constructor which determine the orientation of our axes, based
   // on legacy box properties (-webkit-box-orient, -webkit-box-direction) or
   // modern flexbox properties (flex-direction, flex-wrap) depending on whether
   // the flex container is a "legacy box" (as determined by IsLegacyBox).
   void InitAxesFromLegacyProps(const nsFlexContainerFrame* aFlexContainer);
   void InitAxesFromModernProps(const nsFlexContainerFrame* aFlexContainer);
 
   // XXXdholbert [BEGIN DEPRECATED]