diff --git a/layout/generic/WritingModes.h b/layout/generic/WritingModes.h
index 4bace711dab6..19078c023fb7 100644
--- a/layout/generic/WritingModes.h
+++ b/layout/generic/WritingModes.h
@@ -507,6 +507,12 @@ public:
                            aContainerWidth);
   }
 
+  bool operator==(LogicalPoint aOther) const
+  {
+    CHECK_WRITING_MODE(aOther.GetWritingMode());
+    return mPoint == aOther.mPoint;
+  }
+
   LogicalPoint operator+(const LogicalPoint& aOther) const
   {
     CHECK_WRITING_MODE(aOther.GetWritingMode());
@@ -518,6 +524,33 @@ public:
                         mPoint.y + aOther.mPoint.y);
   }
 
+  LogicalPoint& operator+=(const LogicalPoint& aOther)
+  {
+    CHECK_WRITING_MODE(aOther.GetWritingMode());
+    I() += aOther.I();
+    B() += aOther.B();
+    return *this;
+  }
+
+  LogicalPoint operator-(const LogicalPoint& aOther) const
+  {
+    CHECK_WRITING_MODE(aOther.GetWritingMode());
+    // In non-debug builds, LogicalPoint does not store the WritingMode,
+    // so the first parameter here (which will always be eUnknownWritingMode)
+    // is ignored.
+    return LogicalPoint(GetWritingMode(),
+                        mPoint.x - aOther.mPoint.x,
+                        mPoint.y - aOther.mPoint.y);
+  }
+
+  LogicalPoint& operator-=(const LogicalPoint& aOther)
+  {
+    CHECK_WRITING_MODE(aOther.GetWritingMode());
+    I() -= aOther.I();
+    B() -= aOther.B();
+    return *this;
+  }
+
 private:
   friend class LogicalRect;
 
@@ -1320,6 +1353,12 @@ public:
 
   void SetEmpty() { mRect.SetEmpty(); }
 
+  bool IsEqualEdges(const LogicalRect aOther) const
+  {
+    CHECK_WRITING_MODE(aOther.GetWritingMode());
+    return mRect.IsEqualEdges(aOther.mRect);
+  }
+
 /* XXX are these correct?
   nscoord ILeft(WritingMode aWritingMode) const
   {
@@ -1432,17 +1471,17 @@ public:
     }
   }
 
-#if 0 // XXX this would require aContainerWidth as well
   /**
    * Return a LogicalRect representing this rect in a different writing mode
    */
-  LogicalRect ConvertTo(WritingMode aToMode, WritingMode aFromMode) const
+  LogicalRect ConvertTo(WritingMode aToMode, WritingMode aFromMode,
+                        nscoord aContainerWidth) const
   {
     CHECK_WRITING_MODE(aFromMode);
     return aToMode == aFromMode ?
-      *this : LogicalRect(aToMode, GetPhysicalRect(aFromMode));
+      *this : LogicalRect(aToMode, GetPhysicalRect(aFromMode, aContainerWidth),
+                          aContainerWidth);
   }
-#endif
 
 private:
   LogicalRect() MOZ_DELETE;