Speed up updating inner value of HTMLTextFormControlElements.

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()) {
+    HTMLElement* innerEditor = innerEditorElement();
+    if (textIsChanged || innerEditor->hasChildren()) {

[yosin_UTC9, 2015/09/20 12:42:40]

nit: Could you change this to early return style?

[sof, 2015/09/20 13:05:05]

Done.

         if (textIsChanged && layoutObject()) {
             if (AXObjectCache* cache = document().existingAXObjectCache())
                 cache->handleTextFormControlChanged(this);
         }
-        innerEditorElement()->setInnerText(value, ASSERT_NO_EXCEPTION);
+#if ENABLE(OILPAN)
+        // Oilpan: if 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.
+        // There is a slight slowdown without Oilpan on small benchmarks,
+        // hence not checked for & done there.
+        if (isHTMLBRElement(innerEditor->lastChild()))
+            innerEditor->removeChild(innerEditor->lastChild(), ASSERT_NO_EXCEPTION);
+#endif
+
+        innerEditor->setInnerText(value, ASSERT_NO_EXCEPTION);
 
         if (value.endsWith('\n') || value.endsWith('\r'))
-            innerEditorElement()->appendChild(HTMLBRElement::create(document()));
+            innerEditor->appendChild(HTMLBRElement::create(document()));
     }
 }
 
 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