update3dRenderingContext is 13.5% of GraphicsLayerUpdater::rebuildTree

Source/core/rendering/RenderLayer.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple Inc. All rights reserved.
  *
  * Portions are Copyright (C) 1998 Netscape Communications Corporation.
  *
  * Other contributors:
  *   Robert O'Callahan <roc+@cs.cmu.edu>
  *   David Baron <dbaron@fas.harvard.edu>
  *   Christian Biesinger <cbiesinger@web.de>
  *   Randall Jesup <rjesup@wgate.com>
@@ skipping 118 matching lines @@
     , m_needsToRecomputeBounds(true)
     , m_renderer(renderer)
     , m_parent(0)
     , m_previous(0)
     , m_next(0)
     , m_first(0)
     , m_last(0)
     , m_staticInlinePosition(0)
     , m_staticBlockPosition(0)
     , m_enclosingPaginationLayer(0)
-    , m_3dRenderingContextRoot(0)
     , m_groupedMapping(0)
     , m_repainter(renderer)
     , m_clipper(renderer)
     , m_blendInfo(renderer)
 {
     updateStackingNode();
 
     m_isSelfPaintingLayer = shouldBeSelfPaintingLayer();
 
     if (!renderer->firstChild() && renderer->style()) {
@@ skipping 405 matching lines @@
         ASSERT(box);
         m_transform->makeIdentity();
         box->style()->applyTransform(*m_transform, box->pixelSnappedBorderBoxRect().size(), RenderStyle::IncludeTransformOrigin);
         makeMatrixRenderable(*m_transform, canRender3DTransforms());
     }
 
     if (had3DTransform != has3DTransform())
         dirty3DTransformedDescendantStatus();
 }
 
-// Note: this function assumes that all ancestors have an updated 3d rendering context root.
-void RenderLayer::update3dRenderingContext()
+static RenderLayer* enclosingLayerForContainingBlock(RenderLayer* layer)
 {
-    m_3dRenderingContextRoot = 0;
+    if (RenderObject* containingBlock = layer->renderer()->containingBlock())
+        return containingBlock->enclosingLayer();
+    return 0;
+}
 
-    if (!shouldFlattenTransform())
-        m_3dRenderingContextRoot = this;
+RenderLayer* RenderLayer::renderingContextRoot()
+{
+    RenderLayer* renderingContext = 0;
 
-    if (RenderObject* containingBlock = renderer()->containingBlock()) {
-        if (RenderLayer* ancestorLayer = containingBlock->enclosingLayer()) {
-            if (!ancestorLayer->shouldFlattenTransform())
-                m_3dRenderingContextRoot = ancestorLayer->renderingContextRoot();
-        }
-    }
+    if (shouldPreserve3D())
+        renderingContext = this;
+
+    for (RenderLayer* current = enclosingLayerForContainingBlock(this); current && current->shouldPreserve3D(); current = enclosingLayerForContainingBlock(current))
+        renderingContext = current;
+
+    return renderingContext;
 }
 
 TransformationMatrix RenderLayer::currentTransform(RenderStyle::ApplyTransformOrigin applyOrigin) const
 {
     if (!m_transform)
         return TransformationMatrix();
 
     // m_transform includes transform-origin, so we need to recompute the transform here.
     if (applyOrigin == RenderStyle::ExcludeTransformOrigin) {
         RenderBox* box = renderBox();
@@ skipping 3590 matching lines @@
     }
 }
 
 void showLayerTree(const WebCore::RenderObject* renderer)
 {
     if (!renderer)
         return;
     showLayerTree(renderer->enclosingLayer());
 }
 #endif