Speed up updating inner value of HTMLTextFormControlElements.

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

Index: third_party/WebKit/Source/core/html/HTMLTextFormControlElement.cpp
diff --git a/third_party/WebKit/Source/core/html/HTMLTextFormControlElement.cpp b/third_party/WebKit/Source/core/html/HTMLTextFormControlElement.cpp
index 1c8fbe9798b18ed838a2e587644dbb5964e85eab..91fddfec1b329d7b8ba4011690317e850de83236 100644
--- a/third_party/WebKit/Source/core/html/HTMLTextFormControlElement.cpp
+++ b/third_party/WebKit/Source/core/html/HTMLTextFormControlElement.cpp
@@ -632,15 +632,25 @@ void HTMLTextFormControlElement::setInnerEditorValue(const String& value)
         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 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 (value.endsWith('\n') || value.endsWith('\r'))
-            innerEditorElement()->appendChild(HTMLBRElement::create(document()));
+    if (textIsChanged && layoutObject()) {
+        if (AXObjectCache* cache = document().existingAXObjectCache())
+            cache->handleTextFormControlChanged(this);
     }
 }