Untangle multicol coordinate space conversion from offsetFromContainer().

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

 /*
  * Copyright (C) 2004, 2008, 2009, 2010 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
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 64 matching lines @@
 
     ASSERT(caretLayoutItem.isDescendantOf(caretPainterItem));
 
     bool unrooted = false;
     while (caretLayoutItem != caretPainterItem) {
         LayoutItem containerItem = caretLayoutItem.container();
         if (containerItem.isNull()) {
             unrooted = true;
             break;
         }
-        caretRect.move(caretLayoutItem.offsetFromContainer(containerItem, caretRect.location()));
+        caretRect.move(caretLayoutItem.offsetFromContainer(containerItem));
+
+        // TODO(mstensho): Fix crbug.com/596070 and get rid of this flowthread/multicol thing
+        // here. It was added to keep the same behavior as before flowthread-to-visual coordinate
+        // space conversion was moved out from offsetFromContainer() to mapLocalToAncestor().
+        LayoutObject* containerObject = (LayoutObject*)containerItem;

[mstensho (USE GERRIT), 2016/03/18 20:51:40]

Pretty sure I'm violating the API encapsulation like a real h4x0r here. :) The
other option would be to add a temporary method to the LayoutItem API, but that
seems silly, since the patch that removes this code is more or less ready to be
filed already.

[leviw_travelin_and_unemployed, 2016/03/18 22:27:02]

Really you should be adding that method to the API here. It's not so bad :)

[mstensho (USE GERRIT), 2016/03/18 22:45:23]

Done.

+        if (containerObject->isLayoutFlowThread())
+            caretRect.move(containerObject->columnOffset(caretRect.location()));
+
         caretLayoutItem = containerItem;
     }
 
     if (unrooted)
         caretRect = LayoutRect();
 }
 
 bool CaretBase::updateCaretRect(const PositionWithAffinity& caretPosition)
 {
     m_caretLocalRect = LayoutRect();
@@ skipping 98 matching lines @@
     else
         element = node->parentElement();
 
     if (element && element->layoutObject())
         caretColor = element->layoutObject()->resolveColor(CSSPropertyColor);
 
     context.fillRect(FloatRect(drawingRect), caretColor);
 }
 
 } // namespace blink