Don't apply container flip when computing offset to transformed ancestor.

third_party/WebKit/Source/core/layout/LayoutObject.h

 /*
  * Copyright (C) 2000 Lars Knoll (knoll@kde.org)
  *           (C) 2000 Antti Koivisto (koivisto@kde.org)
  *           (C) 2000 Dirk Mueller (mueller@kde.org)
  *           (C) 2004 Allan Sandfeld Jensen (kde@carewolf.com)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
@@ skipping 75 matching lines @@
 };
 
 enum MarkingBehavior {
     MarkOnlyThis,
     MarkContainerChain,
 };
 
 enum MapCoordinatesMode {
     IsFixed = 1 << 0,
     UseTransforms = 1 << 1,
+
+    // When walking up the containing block chain, applies a container flip for the first
+    // element found, if any, for which isFlippedBlocksWritingMode is true. This option should
+    // generally be used when mapping a source rect in a logical space to one in a physical

[Xianzhu, 2016/05/06 22:25:04]

"logical space" is not accurate. It's the third coordinate space ('physical
coordinates with flipped block-flow direction') described in the doc of
LayoutBoxModelObject.

[chrishtr, 2016/05/09 16:47:43]

Done.

+    // destination space.
     ApplyContainerFlip = 1 << 2,
     TraverseDocumentBoundaries = 1 << 3,
 
     // Applies to LayoutView::mapLocalToAncestor() and LayoutView::mapToVisualRectInAncestorSpace()
     // only, to indicate the input point or rect is in frame coordinates instead of frame contents
     // coordinates. This disables view clipping and scroll offset adjustment.
     // TODO(wangxianzhu): Remove this when root-layer-scrolls launches.
     InputIsInFrameCoordinates = 1 << 4,
 };
 typedef unsigned MapCoordinatesFlags;
@@ skipping 2066 matching lines @@
 void showTree(const blink::LayoutObject*);
 void showLineTree(const blink::LayoutObject*);
 void showLayoutTree(const blink::LayoutObject* object1);
 // We don't make object2 an optional parameter so that showLayoutTree
 // can be called from gdb easily.
 void showLayoutTree(const blink::LayoutObject* object1, const blink::LayoutObject* object2);
 
 #endif
 
 #endif // LayoutObject_h