Plumb selection bounds as a single unit

public/platform/WebSelectionBound.h

Index: public/platform/WebSelectionBound.h
diff --git a/public/platform/WebSelectionBound.h b/public/platform/WebSelectionBound.h
index bdedd3636e685e4a8cff8b5c1e863b384057f490..466a39cc0a08eee6e3f6590858c46199a8956884 100644
--- a/public/platform/WebSelectionBound.h
+++ b/public/platform/WebSelectionBound.h
@@ -11,6 +11,8 @@ 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,
@@ -20,6 +22,7 @@ struct WebSelectionBound {
     explicit WebSelectionBound(Type type)
         : type(type)
         , layerId(0)
+        , isTextDirectionRTL(false)
     {
     }
 
@@ -34,6 +37,9 @@ struct WebSelectionBound {
     // that define the selection bound.
     WebPoint edgeTopInLayer;
     WebPoint edgeBottomInLayer;
+
+    // Whether the text direction at this location is RTL.
+    bool isTextDirectionRTL;
 };
 
 } // namespace blink