Dispose temporary and not-cached Range in DOMSelection

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

 /*
  * Copyright (C) 2007, 2009 Apple Inc. All rights reserved.
  * Copyright (C) 2012 Google 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.
@@ skipping 520 matching lines @@
 
   if (Range* cachedRange = documentCachedRange())
     return cachedRange;
 
   Range* range = createRange(createRangeFromSelectionEditor());
   cacheRangeIfSelectionOfDocument(range);
   return range;
 }
 
 Range* DOMSelection::primaryRangeOrNull() const {
-  return rangeCount() > 0 ? getRangeAt(0, ASSERT_NO_EXCEPTION) : nullptr;
+  if (rangeCount() <= 0)
+    return nullptr;
+  Range* range = getRangeAt(0, ASSERT_NO_EXCEPTION);
+  if (!isSelectionOfDocument())

[yosin_UTC9, 2017/04/04 04:50:07]

I'm not a fan of this approach. We still create temporary Range.
Disposing it doesn't make execution speed, but we still have temporary object
eating GC heap up.

[yoichio, 2017/04/04 05:32:42]

Creating temporary Ranges and Disposing them is different matter.
At least disposing Range from document makes tree modification 
 faster though temporary Range is in heap.

I will implement somehow there is cached Range for each TreeScope 
 later.

[yosin_UTC9, 2017/04/04 07:21:31]

Calling Range::dispose() is error prone in this case and hacky.
Let's make clear code rather hacky code.

[tkent, 2017/04/04 08:41:24]

I agree that it's a hack :)
If we have no reason to be hurry, we should avoid this approach.

+    range->dispose();
+  return range;
 }
 
 EphemeralRange DOMSelection::createRangeFromSelectionEditor() const {
   const VisibleSelection& selection = visibleSelection();
   const Position& anchor = blink::anchorPosition(selection);
   if (isSelectionOfDocument() && !anchor.anchorNode()->isInShadowTree())
     return firstEphemeralRangeOf(selection);
 
   Node* const anchorNode = shadowAdjustedNode(anchor);
   if (!anchorNode)  // crbug.com/595100
@@ skipping 270 matching lines @@
     m_treeScope->document().addConsoleMessage(
         ConsoleMessage::create(JSMessageSource, ErrorMessageLevel, message));
 }
 
 DEFINE_TRACE(DOMSelection) {
   visitor->trace(m_treeScope);
   ContextClient::trace(visitor);
 }
 
 }  // namespace blink