Plumb selection bounds as a single unit

public/platform/WebSelectionBound.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef WebSelectionBound_h
 #define WebSelectionBound_h
 
 #include "public/platform/WebPoint.h"
 
 namespace blink {
 
 // An endpoint for an active selection region.
 struct WebSelectionBound {
+    // TODO(jdduke): Remove this logic when downstream code adopts
+    // |WebSelection| for determining bound orientation.
     enum Type {
         Caret,
         SelectionLeft,
         SelectionRight
     };
 
     explicit WebSelectionBound(Type type)
         : type(type)
         , layerId(0)
+        , isTextDirectionRTL(false)
     {
     }
 
     // The logical type of the endpoint. Note that this is dependent not only on
     // the bound's relative location, but also the underlying text direction.
     Type type;
 
     // The id of the platform layer to which the bound should be anchored.
     int layerId;
 
     // The bottom and top coordinates of the edge (caret), in layer coordinates,
     // that define the selection bound.
     WebPoint edgeTopInLayer;
     WebPoint edgeBottomInLayer;
+
+    // Whether the text direction at this location is RTL.
+    bool isTextDirectionRTL;
 };
 
 } // namespace blink
 
 #endif