Speed up updating inner value of HTMLTextFormControlElements.

third_party/WebKit/Source/core/html/HTMLTextFormControlElement.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007 Apple Inc. All rights reserved.
  *           (C) 2006 Alexey Proskuryakov (ap@nypop.com)
  *
  * 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
@@ skipping 614 matching lines @@
     return m_lastChangeWasUserEdit;
 }
 
 void HTMLTextFormControlElement::setInnerEditorValue(const String& value)
 {
     ASSERT(!openShadowRoot());
     if (!isTextFormControl() || openShadowRoot())
         return;
 
     bool textIsChanged = value != innerEditorValue();
-    if (textIsChanged || !innerEditorElement()->hasChildren()) {
-        if (textIsChanged && layoutObject()) {
-            if (AXObjectCache* cache = document().existingAXObjectCache())
-                cache->handleTextFormControlChanged(this);
-        }
-        innerEditorElement()->setInnerText(value, ASSERT_NO_EXCEPTION);
+    HTMLElement* innerEditor = innerEditorElement();
+    if (!textIsChanged && innerEditor->hasChildren())
+        return;
 
-        if (value.endsWith('\n') || value.endsWith('\r'))
-            innerEditorElement()->appendChild(HTMLBRElement::create(document()));
+    // If the last child is a trailing <br> that's appended below, remove it
+    // first so as to enable setInnerText() fast path of updating a text node,
+    // requiring less allocations. Generally helpful, but avoids dead object

[esprehn, 2015/09/25 18:34:37]

I would remove the comment about less allocations and the mention of Oilpan.
This seems like a reasonable thing to do in general.

"fast path of updating a text node."

[sof, 2015/09/26 06:20:23]

Done.

+    // buildup with Oilpan on benchmarks pounding this update operation.
+    if (isHTMLBRElement(innerEditor->lastChild()))
+        innerEditor->removeChild(innerEditor->lastChild(), ASSERT_NO_EXCEPTION);
+
+    innerEditor->setInnerText(value, ASSERT_NO_EXCEPTION);
+
+    if (value.endsWith('\n') || value.endsWith('\r'))
+        innerEditor->appendChild(HTMLBRElement::create(document()));
+
+    if (textIsChanged && layoutObject()) {
+        if (AXObjectCache* cache = document().existingAXObjectCache())
+            cache->handleTextFormControlChanged(this);
     }
 }
 
 static String finishText(StringBuilder& result)
 {
     // Remove one trailing newline; there's always one that's collapsed out by layoutObject.
     size_t size = result.length();
     if (size && result[size - 1] == '\n')
         result.resize(--size);
     return result.toString();
@@ skipping 353 matching lines @@
 }
 
 void HTMLTextFormControlElement::copyNonAttributePropertiesFromElement(const Element& source)
 {
     const HTMLTextFormControlElement& sourceElement = static_cast<const HTMLTextFormControlElement&>(source);
     m_lastChangeWasUserEdit = sourceElement.m_lastChangeWasUserEdit;
     HTMLFormControlElement::copyNonAttributePropertiesFromElement(source);
 }
 
 } // namespace blink