Brush up localSelectionRectOfPositionTemplate

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

 /*
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009 Apple Inc. All rights
  * reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 2546 matching lines @@
 // using the line top value instead of the selection top.
 template <typename Strategy>
 LayoutRect localSelectionRectOfPositionTemplate(
     const PositionWithAffinityTemplate<Strategy>& position,
     LayoutObject*& layoutObject) {
   LayoutRect rect = localCaretRectOfPositionTemplate(position, layoutObject);
 
   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());
     return rect;
   }
 
   rect.setX(box->root().selectionTop());
   rect.setWidth(box->root().selectionHeight());
   return rect;
 }
@@ skipping 1321 matching lines @@
 
 VisiblePositionInFlatTree previousPositionOf(
     const VisiblePositionInFlatTree& visiblePosition,
     EditingBoundaryCrossingRule rule) {
   DCHECK(visiblePosition.isValid()) << visiblePosition;
   return previousPositionOfAlgorithm<EditingInFlatTreeStrategy>(
       visiblePosition.deepEquivalent(), rule);
 }
 
 }  // namespace blink