Avoid allocating temporary ranges in connection with text and character iterators.

Source/core/editing/PlainTextRange.cpp

 /*
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2005 Alexey Proskuryakov.
  *
  * 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 69 matching lines @@
 
     TextIteratorBehaviorFlags behaviorFlags = TextIteratorEmitsObjectReplacementCharacter;
     if (getRangeFor == ForSelection)
         behaviorFlags |= TextIteratorEmitsCharactersBetweenAllVisiblePositions;
     TextIterator it(rangeOfContents(const_cast<ContainerNode*>(&scope)).get(), behaviorFlags);
 
     // FIXME: the atEnd() check shouldn't be necessary, workaround for <http://bugs.webkit.org/show_bug.cgi?id=6289>.
     if (!start() && !length() && it.atEnd()) {
         textRunRange = it.range();
 
-        resultRange->setStart(textRunRange->startContainer(), 0, ASSERT_NO_EXCEPTION);
+        resultRange->setStart(it.startContainer(), 0, ASSERT_NO_EXCEPTION);
         resultRange->setEnd(textRunRange->startContainer(), 0, ASSERT_NO_EXCEPTION);

[yosin_UTC9, 2014/09/08 01:55:19]

nit: It seems we can replace L91 |textRunRange->startContainer()| to
|it.startContainer()| as L90.

If so, we can get rid of |Range| object creation at |it.range()|.

TODO: We should rename |TextIterator::range()| to |CreateRange()| or another to
indicate this is expensive operation rather than accessing cheap property
access.

[Mads Ager (chromium), 2014/09/08 08:50:46]

Yes, good catch, not sure why I didn't notice that. Thanks!
 
Yes, we should.

 
         return resultRange.release();
     }
 
     for (; !it.atEnd(); it.advance()) {
         int len = it.length();
         textRunRange = it.range();
 
         bool foundStart = start() >= docTextPosition && start() <= docTextPosition + len;
         bool foundEnd = end() >= docTextPosition && end() <= docTextPosition + len;
@@ skipping 77 matching lines @@
     size_t start = TextIterator::rangeLength(testRange.get());
 
     testRange->setEnd(range.endContainer(), range.endOffset(), IGNORE_EXCEPTION);
     ASSERT(testRange->startContainer() == &scope);
     size_t end = TextIterator::rangeLength(testRange.get());
 
     return PlainTextRange(start, end);
 }
 
 }