Brush up localSelectionRectOfPositionTemplate

third_party/WebKit/Source/core/editing/VisibleUnits.cpp

Index: third_party/WebKit/Source/core/editing/VisibleUnits.cpp
diff --git a/third_party/WebKit/Source/core/editing/VisibleUnits.cpp b/third_party/WebKit/Source/core/editing/VisibleUnits.cpp
index 7551fa9aca421a97db3626f5ab5ffe45be2a8c94..63dfc47add6113e7ef59cbe2db62ed821a8af7f6 100644
--- a/third_party/WebKit/Source/core/editing/VisibleUnits.cpp
+++ b/third_party/WebKit/Source/core/editing/VisibleUnits.cpp
@@ -2564,10 +2564,10 @@ LayoutRect localSelectionRectOfPositionTemplate(
   if (rect.isEmpty())
     return rect;
 
-  InlineBoxPosition boxPosition =
+  const InlineBoxPosition boxPosition =
       computeInlineBoxPosition(position.position(), position.affinity());
 
-  InlineTextBox* box = toInlineTextBox(boxPosition.inlineBox);
+  InlineBox* const box = boxPosition.inlineBox;

[yosin_UTC9, 2017/01/20 05:59:53]

Please see also https://codereview.chromium.org/2636623002
If we can get base line for non-InlineTextBox, it is good!

   if (layoutObject->style()->isHorizontalWritingMode()) {
     rect.setY(box->root().selectionTop());
     rect.setHeight(box->root().selectionHeight());