Use FrameSelection::selectedText where possible.

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

 /*
  * Copyright (C) 2004, 2005, 2006 Apple Computer, 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 251 matching lines @@
     // tested, which make style determinations based on the first character of
     // the selection. For instance, this operation helps to make sure that the
     // "X" selected below is the only thing selected. The range should not be
     // allowed to "leak" out to the end of the previous text node, or to the
     // beginning of the next text node, each of which has a different style.
     //
     // On a treasure map, <b>X</b> marks the spot.
     //                       ^ selected
     //
     ASSERT(isRange());
-    return normalizeRange(EphemeralRange(m_start, m_end));
+    const EphemeralRange range(m_start, m_end);
+    return range.isNotNull() ? normalizeRange(range) : range;

[yosin_UTC9, 2015/10/01 06:29:09]

Why do you check |range.isNotNull()|?
If |isRange()| is true, |range| can't be null.

[kotenkov, 2015/10/02 08:28:07]

Yes, you are right. Now I understand that I should check for |isRange()| in
|extractSelectedTextAlgorithm()| and |extractSelectedHTMLAlgorithm()|. As I did
not check it in the first patchset, I had to check for |isNotNull()| here. That
was clearly a mistake.

 }
 
 bool VisibleSelection::expandUsingGranularity(TextGranularity granularity)
 {
     if (isNone())
         return false;
 
     // FIXME: Do we need to check all of them?
     Position oldBase = m_base;
     Position oldExtent = m_extent;
@@ skipping 882 matching lines @@
 }
 
 template <typename Strategy>
 VisibleSelectionTemplate<Strategy>::VisibleSelectionTemplate()
 {
 }
 
 template <typename Strategy>
 EphemeralRangeTemplate<Strategy> VisibleSelectionTemplate<Strategy>::toNormalizedEphemeralRange() const
 {
-    return normalizeRange(EphemeralRangeTemplate<Strategy>(start(), end()));
+    const EphemeralRangeTemplate<Strategy> range(start(), end());

[yosin_UTC9, 2015/10/01 06:29:09]

Do you have a case we call |toNormalizedEphemeralRange()| with empty selection?

If we have a such case, let's make |normalizeRange()| to handle null
case rather than each call site.

[kotenkov, 2015/10/02 08:28:07]

No, it seems, that we should only call |toNormalizedEphemeralRange()| if
|isRange()| is true and in that case the range cannot be null.

+    return range.isNotNull() ? normalizeRange(range) : range;
 }
 
 template <typename Strategy>
 void VisibleSelectionTemplate<Strategy>::setBase(const VisiblePositionTemplate<Strategy>& newBase)
 {
     return setBase(newBase.deepEquivalent());
 }
 
 template <typename Strategy>
 void VisibleSelectionTemplate<Strategy>::setExtent(const VisiblePositionTemplate<Strategy>& newExtent)
@@ skipping 219 matching lines @@
     sel.showTreeForThis();
 }
 
 void showTree(const blink::VisibleSelection* sel)
 {
     if (sel)
         sel->showTreeForThis();
 }
 
 #endif