Speed up updating inner value of HTMLTextFormControlElements.

Source/core/html/HTMLTextFormControlElement.cpp

Index: Source/core/html/HTMLTextFormControlElement.cpp
diff --git a/Source/core/html/HTMLTextFormControlElement.cpp b/Source/core/html/HTMLTextFormControlElement.cpp
index 1c8fbe9798b18ed838a2e587644dbb5964e85eab..63b2398d2e66b99966a7e48eb55b0d44c985f68d 100644
--- a/Source/core/html/HTMLTextFormControlElement.cpp
+++ b/Source/core/html/HTMLTextFormControlElement.cpp
@@ -632,15 +632,26 @@ void HTMLTextFormControlElement::setInnerEditorValue(const String& value)
         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()));
     }
 }