Bug 1174003 part 11: [css-flexbox] Remove IsCrossAxisHorizontal(), and make IsMainAxisHorizontal() a private implementation detail. r=mats

At this point in the series:
 - AxisOrientationTracker::IsCrossAxisHorizontal() has zero callers, so it can
   be deleted.
 - AxisOrientationTracker::IsMainAxisHorizontal() only has two callers, and
   both are inside its own class. So it's effectively become an implementation
   detail of its class, and it can be made private.  (I'm not entirely removing
   it, because it does make its two callers more readable. The callers are
   working with a physical-axis-dependent type, 'LayoutDeviceIntSize', which
   comes from an API that isn't logical-axis-friendly, "GetMinimumWidgetSize",
   so they're not easily logicalized. So: it's nice to keep
   IsMainAxisHorizontal() around as an internal convenience method to tell us
   whether to extract the width or height inside of these two specific
   methods. But we don't want to introduce more callers, so let's leave it
   around & make it private.)

MozReview-Commit-ID: 1iz1e52NmxV

--HG--
extra : rebase_source : e8e92bbaadb5b8e636bd1dda79cb0041ce36a2ea

layout/generic/nsFlexContainerFrame.cpp

@@ -294,16 +294,6 @@ public:
   // 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.
@@ -412,6 +402,15 @@ private:
   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