Resolve flickering the text selection when hitting culled inline.

Source/core/rendering/RenderInline.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009 Apple 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
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
@@ skipping 817 matching lines @@
         result.addNodeToRectBasedTestResult(node(), request, locationInContainer);
         return regionResult.contains(tmpLocation.boundingBox());
     }
     return false;
 }
 
 PositionWithAffinity RenderInline::positionForPoint(const LayoutPoint& point)
 {
     // FIXME: Does not deal with relative positioned inlines (should it?)
     RenderBlock* cb = containingBlock();
-    if (firstLineBox()) {
+    if (firstLineBoxIncludingCulling()) {

[pdr., 2015/02/16 20:24:09]

There are 35 other callers of firstLineBox(). Is this the only one that needs to
be changed? How do we know which to use?

[Miyoung Shin(g), 2015/02/17 05:01:54]

We need only this to solve the problem that flickers on the text selection.
But I'm not sure if we need to change firstLineBox to
firstLineBoxIncludingCulling more for other cases.
IMHO, we should choose firstLineBoxIncludingCulling() if we want to calculate
the position such as offsetLeft() and generateLineBoxRects().
But we don't need to use it for the painting job.
For example,
I think we don't need to use firstLineBoxIncludingCulling in
RenderInline::invalidateDisplayItemClients,
because culled inline doesn't have own displaying area.

As you said, there are many other callers of firstLineBox(),
but I can see to branch out the code flow between the normal inline and culled
inline using alwaysCreateLineBoxes() in almost places calling firstLineBox().

For example.
RenderInline::linesBoundingBox() {
...
    if (!alwaysCreateLineBoxes()) {
	...
	}
..
}

If my comment is not clear, let me know.

         // This inline actually has a line box.  We must have clicked in the border/padding of one of these boxes.  We
         // should try to find a result by asking our containing block.
         return cb->positionForPoint(point);
     }
 
     // Translate the coords from the pre-anonymous block to the post-anonymous block.
     LayoutPoint parentBlockPoint = cb->location() + point;
     RenderBoxModelObject* c = continuation();
     while (c) {
         RenderBox* contBlock = c->isInline() ? c->containingBlock() : toRenderBlock(c);
@@ skipping 603 matching lines @@
 }
 
 void RenderInline::invalidateDisplayItemClients(DisplayItemList* displayItemList) const
 {
     RenderBoxModelObject::invalidateDisplayItemClients(displayItemList);
     for (InlineFlowBox* box = firstLineBox(); box; box = box->nextLineBox())
         displayItemList->invalidate(box->displayItemClient());
 }
 
 } // namespace blink