Make compositing updates 30.7% faster for calculator

Source/core/rendering/compositing/CompositingPropertyUpdater.cpp

Index: Source/core/rendering/compositing/CompositingPropertyUpdater.cpp
diff --git a/Source/core/rendering/compositing/CompositingPropertyUpdater.cpp b/Source/core/rendering/compositing/CompositingPropertyUpdater.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..6e86d2df66216872d10ffb634c5be362c66c691f
--- /dev/null
+++ b/Source/core/rendering/compositing/CompositingPropertyUpdater.cpp
@@ -0,0 +1,48 @@
+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "config.h"
+#include "core/rendering/compositing/CompositingPropertyUpdater.h"
+
+#include "core/rendering/RenderLayer.h"
+
+namespace WebCore {
+
+CompositingPropertyUpdater::CompositingPropertyUpdater()
+    : m_geometryMap(UseTransforms)
+{
+}
+
+CompositingPropertyUpdater::~CompositingPropertyUpdater()
+{
+}
+
+void CompositingPropertyUpdater::updateAncestorDependentProperties(RenderLayer* layer, UpdateType updateType)
+{
+    if (!layer->decendantNeedsToUpdateAncestorDependentProperties() && updateType != ForceUpdate)
+        return;
+
+    m_geometryMap.pushMappingsToAncestor(layer, layer->parent());
+
+    if (layer->needsToUpdateAncestorDependentProperties())
+        updateType = ForceUpdate;
+
+    if (updateType == ForceUpdate) {
+        RenderLayer::AncestorDependentProperties properties;
+
+        if (!layer->isRootLayer())
+            properties.absoluteBoundingBox = enclosingIntRect(m_geometryMap.absoluteRect(layer->overlapBounds()));
+
+        layer->updateAncestorDependentProperties(properties);
+    }
+
+    for (RenderLayer* child = layer->firstChild(); child; child = child->nextSibling())
+        updateAncestorDependentProperties(child, updateType);
+
+    layer->clearDecendantNeedsToUpdateAncestorDependentProperties();

[ojan, 2014/03/27 01:06:42]

Nit: I'd put this line at the very end of this function.

[abarth-chromium, 2014/03/27 01:40:11]

Ok.  Maybe I should make a RAII for the geometry map pushing/popping.

+
+    m_geometryMap.popMappingsToAncestor(layer->parent());
+}
+
+} // namespace WebCore