Separate the geometry update from rebuilding the GraphicsLayer tree

Source/core/rendering/compositing/RenderLayerCompositor.cpp

Index: Source/core/rendering/compositing/RenderLayerCompositor.cpp
diff --git a/Source/core/rendering/compositing/RenderLayerCompositor.cpp b/Source/core/rendering/compositing/RenderLayerCompositor.cpp
index 2a9c12170d1616ff321ebccb49347c4037584779..c6b6e8372ee34751f1041ff914ad267d2c763509 100644
--- a/Source/core/rendering/compositing/RenderLayerCompositor.cpp
+++ b/Source/core/rendering/compositing/RenderLayerCompositor.cpp
@@ -58,6 +58,7 @@
 #include "core/rendering/RenderVideo.h"
 #include "core/rendering/RenderView.h"
 #include "core/rendering/compositing/CompositedLayerMapping.h"
+#include "core/rendering/compositing/CompositingRequirementsUpdater.h"
 #include "core/rendering/compositing/GraphicsLayerUpdater.h"
 #include "platform/OverscrollTheme.h"
 #include "platform/TraceEvent.h"
@@ -75,134 +76,6 @@ namespace WebCore {
 
 using namespace HTMLNames;
 
-class OverlapMapContainer {
-public:
-    void add(const IntRect& bounds)
-    {
-        m_layerRects.append(bounds);
-        m_boundingBox.unite(bounds);
-    }
-
-    bool overlapsLayers(const IntRect& bounds) const
-    {
-        // Checking with the bounding box will quickly reject cases when
-        // layers are created for lists of items going in one direction and
-        // never overlap with each other.
-        if (!bounds.intersects(m_boundingBox))
-            return false;
-        for (unsigned i = 0; i < m_layerRects.size(); i++) {
-            if (m_layerRects[i].intersects(bounds))
-                return true;
-        }
-        return false;
-    }
-
-    void unite(const OverlapMapContainer& otherContainer)
-    {
-        m_layerRects.appendVector(otherContainer.m_layerRects);
-        m_boundingBox.unite(otherContainer.m_boundingBox);
-    }
-private:
-    Vector<IntRect, 64> m_layerRects;
-    IntRect m_boundingBox;
-};
-
-class RenderLayerCompositor::OverlapMap {
-    WTF_MAKE_NONCOPYABLE(OverlapMap);
-public:
-    OverlapMap()
-    {
-        // Begin by assuming the root layer will be composited so that there
-        // is something on the stack. The root layer should also never get a
-        // finishCurrentOverlapTestingContext() call.
-        beginNewOverlapTestingContext();
-    }
-
-    void add(RenderLayer* layer, const IntRect& bounds)
-    {
-        if (layer->isRootLayer() || bounds.isEmpty())
-            return;
-
-        // Layers do not contribute to overlap immediately--instead, they will
-        // contribute to overlap as soon as they have been recursively processed
-        // and popped off the stack.
-        ASSERT(m_overlapStack.size() >= 2);
-        m_overlapStack[m_overlapStack.size() - 2].add(bounds);
-    }
-
-    bool overlapsLayers(const IntRect& bounds) const
-    {
-        return m_overlapStack.last().overlapsLayers(bounds);
-    }
-
-    void beginNewOverlapTestingContext()
-    {
-        // This effectively creates a new "clean slate" for overlap state.
-        // This is used when we know that a subtree or remaining set of
-        // siblings does not need to check overlap with things behind it.
-        m_overlapStack.append(OverlapMapContainer());
-    }
-
-    void finishCurrentOverlapTestingContext()
-    {
-        // The overlap information on the top of the stack is still necessary
-        // for checking overlap of any layers outside this context that may
-        // overlap things from inside this context. Therefore, we must merge
-        // the information from the top of the stack before popping the stack.
-        //
-        // FIXME: we may be able to avoid this deep copy by rearranging how
-        //        overlapMap state is managed.
-        m_overlapStack[m_overlapStack.size() - 2].unite(m_overlapStack.last());
-        m_overlapStack.removeLast();
-    }
-
-private:
-    Vector<OverlapMapContainer> m_overlapStack;
-};
-
-struct CompositingRecursionData {
-    CompositingRecursionData(RenderLayer* compAncestor, RenderLayer* mostRecentCompositedLayer, bool testOverlap)
-        : m_compositingAncestor(compAncestor)
-        , m_mostRecentCompositedLayer(mostRecentCompositedLayer)
-        , m_subtreeIsCompositing(false)
-        , m_hasUnisolatedCompositedBlendingDescendant(false)
-        , m_testingOverlap(testOverlap)
-#ifndef NDEBUG
-        , m_depth(0)
-#endif
-    {
-    }
-
-    CompositingRecursionData(const CompositingRecursionData& other)
-        : m_compositingAncestor(other.m_compositingAncestor)
-        , m_mostRecentCompositedLayer(other.m_mostRecentCompositedLayer)
-        , m_subtreeIsCompositing(other.m_subtreeIsCompositing)
-        , m_hasUnisolatedCompositedBlendingDescendant(other.m_hasUnisolatedCompositedBlendingDescendant)
-        , m_testingOverlap(other.m_testingOverlap)
-#ifndef NDEBUG
-        , m_depth(other.m_depth + 1)
-#endif
-    {
-    }
-
-    RenderLayer* m_compositingAncestor;
-    RenderLayer* m_mostRecentCompositedLayer; // in paint order regardless of hierarchy.
-    bool m_subtreeIsCompositing;
-    bool m_hasUnisolatedCompositedBlendingDescendant;
-    bool m_testingOverlap;
-#ifndef NDEBUG
-    int m_depth;
-#endif
-};
-
-static void clearAncestorDependentPropertyCacheRecursive(RenderLayer* layer)
-{
-    layer->clearAncestorDependentPropertyCache();
-    RenderLayerStackingNodeIterator iterator(*layer->stackingNode(), AllChildren);
-    for (RenderLayer* child = layer->firstChild(); child; child = child->nextSibling())
-        clearAncestorDependentPropertyCacheRecursive(child);
-}
-
 RenderLayerCompositor::RenderLayerCompositor(RenderView& renderView)
     : m_renderView(renderView)
     , m_compositingReasonFinder(renderView)
@@ -452,11 +325,7 @@ void RenderLayerCompositor::updateIfNeeded()
     RenderLayer* updateRoot = rootRenderLayer();
 
     if (needCompositingRequirementsUpdate) {
-        // Go through the layers in presentation order, so that we can compute which RenderLayers need compositing layers.
-        // FIXME: we could maybe do this and the hierarchy udpate in one pass, but the parenting logic would be more complex.
-        CompositingRecursionData recursionData(updateRoot, 0, true);
         bool layersChanged = false;
-        bool saw3DTransform = false;
 
         {
             TRACE_EVENT0("blink_rendering", "CompositingPropertyUpdater::updateAncestorDependentProperties");
@@ -466,18 +335,7 @@ void RenderLayerCompositor::updateIfNeeded()
 #endif
         }
 
-        {
-            TRACE_EVENT0("blink_rendering", "RenderLayerCompositor::computeCompositingRequirements");
-            OverlapMap overlapTestRequestMap;
-
-            // FIXME: Passing these unclippedDescendants down and keeping track
-            // of them dynamically, we are requiring a full tree walk. This
-            // should be removed as soon as proper overlap testing based on
-            // scrolling and animation bounds is implemented (crbug.com/252472).
-            Vector<RenderLayer*> unclippedDescendants;
-            IntRect absoluteDecendantBoundingBox;
-            computeCompositingRequirements(0, updateRoot, overlapTestRequestMap, recursionData, saw3DTransform, unclippedDescendants, absoluteDecendantBoundingBox);
-        }
+        CompositingRequirementsUpdater(m_renderView, m_compositingReasonFinder, &m_needsToRecomputeCompositingRequirements).update(updateRoot);
 
         {
             TRACE_EVENT0("blink_rendering", "RenderLayerCompositor::assignLayersToBackings");
@@ -544,28 +402,6 @@ void RenderLayerCompositor::updateIfNeeded()
         InspectorInstrumentation::layerTreeDidChange(page());
 }
 
-static bool requiresCompositing(CompositingReasons reasons)
-{
-    // Any reasons other than overlap or assumed overlap will require the layer to be separately compositing.
-    return reasons & ~CompositingReasonComboSquashableReasons;
-}
-
-static bool requiresSquashing(CompositingReasons reasons)
-{
-    // If the layer has overlap or assumed overlap, but no other reasons, then it should be squashed.
-    return !requiresCompositing(reasons) && (reasons & CompositingReasonComboSquashableReasons);
-}
-
-static bool requiresCompositingOrSquashing(CompositingReasons reasons)
-{
-#ifndef NDEBUG
-    bool fastAnswer = reasons != CompositingReasonNone;
-    bool slowAnswer = requiresCompositing(reasons) || requiresSquashing(reasons);
-    ASSERT(fastAnswer == slowAnswer);
-#endif
-    return reasons != CompositingReasonNone;
-}
-
 void RenderLayerCompositor::addOutOfFlowPositionedLayer(RenderLayer* layer)
 {
     m_outOfFlowPositionedLayers.add(layer);
@@ -876,246 +712,6 @@ void RenderLayerCompositor::layerWillBeRemoved(RenderLayer* parent, RenderLayer*
     setCompositingLayersNeedRebuild();
 }
 
-//  Recurse through the layers in z-index and overflow order (which is equivalent to painting order)
-//  For the z-order children of a compositing layer:
-//      If a child layers has a compositing layer, then all subsequent layers must
-//      be compositing in order to render above that layer.
-//
-//      If a child in the negative z-order list is compositing, then the layer itself
-//      must be compositing so that its contents render over that child.
-//      This implies that its positive z-index children must also be compositing.
-//
-void RenderLayerCompositor::computeCompositingRequirements(RenderLayer* ancestorLayer, RenderLayer* layer, OverlapMap& overlapMap, CompositingRecursionData& currentRecursionData, bool& descendantHas3DTransform, Vector<RenderLayer*>& unclippedDescendants, IntRect& absoluteDecendantBoundingBox)
-{
-    layer->stackingNode()->updateLayerListsIfNeeded();
-
-    // Clear the flag
-    layer->setHasCompositingDescendant(false);
-
-    // Start by assuming this layer will not need to composite.
-    CompositingReasons reasonsToComposite = CompositingReasonNone;
-
-    // First accumulate the straightforward compositing reasons.
-    CompositingReasons directReasons = m_compositingReasonFinder.directReasons(layer, &m_needsToRecomputeCompositingRequirements);
-
-    // Video is special. It's the only RenderLayer type that can both have
-    // RenderLayer children and whose children can't use its backing to render
-    // into. These children (the controls) always need to be promoted into their
-    // own layers to draw on top of the accelerated video.
-    if (currentRecursionData.m_compositingAncestor && currentRecursionData.m_compositingAncestor->renderer()->isVideo())
-        directReasons |= CompositingReasonVideoOverlay;
-
-    if (canBeComposited(layer))
-        reasonsToComposite |= directReasons;
-
-    // Next, accumulate reasons related to overlap.
-    // If overlap testing is used, this reason will be overridden. If overlap testing is not
-    // used, we must assume we overlap if there is anything composited behind us in paint-order.
-    CompositingReasons overlapCompositingReason = currentRecursionData.m_subtreeIsCompositing ? CompositingReasonAssumedOverlap : CompositingReasonNone;
-
-    if (m_renderView.compositorDrivenAcceleratedScrollingEnabled()) {
-        Vector<size_t> unclippedDescendantsToRemove;
-        for (size_t i = 0; i < unclippedDescendants.size(); i++) {
-            RenderLayer* unclippedDescendant = unclippedDescendants.at(i);
-            // If we've reached the containing block of one of the unclipped
-            // descendants, that element is no longer relevant to whether or not we
-            // should opt in. Unfortunately we can't easily remove from the list
-            // while we're iterating, so we have to store it for later removal.
-            if (unclippedDescendant->renderer()->containingBlock() == layer->renderer()) {
-                unclippedDescendantsToRemove.append(i);
-                continue;
-            }
-            if (layer->scrollsWithRespectTo(unclippedDescendant))
-                reasonsToComposite |= CompositingReasonAssumedOverlap;
-        }
-
-        // Remove irrelevant unclipped descendants in reverse order so our stored
-        // indices remain valid.
-        for (size_t i = 0; i < unclippedDescendantsToRemove.size(); i++)
-            unclippedDescendants.remove(unclippedDescendantsToRemove.at(unclippedDescendantsToRemove.size() - i - 1));
-
-        if (reasonsToComposite & CompositingReasonOutOfFlowClipping)
-            unclippedDescendants.append(layer);
-    }
-
-    const IntRect& absBounds = layer->ancestorDependentProperties().clippedAbsoluteBoundingBox;
-    absoluteDecendantBoundingBox = absBounds;
-
-    if (currentRecursionData.m_testingOverlap && !requiresCompositingOrSquashing(directReasons))
-        overlapCompositingReason = overlapMap.overlapsLayers(absBounds) ? CompositingReasonOverlap : CompositingReasonNone;
-
-    reasonsToComposite |= overlapCompositingReason;
-
-    // The children of this layer don't need to composite, unless there is
-    // a compositing layer among them, so start by inheriting the compositing
-    // ancestor with m_subtreeIsCompositing set to false.
-    CompositingRecursionData childRecursionData(currentRecursionData);
-    childRecursionData.m_subtreeIsCompositing = false;
-
-    bool willBeCompositedOrSquashed = canBeComposited(layer) && requiresCompositingOrSquashing(reasonsToComposite);
-    if (willBeCompositedOrSquashed) {
-        // Tell the parent it has compositing descendants.
-        currentRecursionData.m_subtreeIsCompositing = true;
-        // This layer now acts as the ancestor for kids.
-        childRecursionData.m_compositingAncestor = layer;
-
-        // Here we know that all children and the layer's own contents can blindly paint into
-        // this layer's backing, until a descendant is composited. So, we don't need to check
-        // for overlap with anything behind this layer.
-        overlapMap.beginNewOverlapTestingContext();
-        // This layer is going to be composited, so children can safely ignore the fact that there's an
-        // animation running behind this layer, meaning they can rely on the overlap map testing again.
-        childRecursionData.m_testingOverlap = true;
-    }
-
-#if !ASSERT_DISABLED
-    LayerListMutationDetector mutationChecker(layer->stackingNode());
-#endif
-
-    bool anyDescendantHas3DTransform = false;
-    bool willHaveForegroundLayer = false;
-
-    if (layer->stackingNode()->isStackingContainer()) {
-        RenderLayerStackingNodeIterator iterator(*layer->stackingNode(), NegativeZOrderChildren);
-        while (RenderLayerStackingNode* curNode = iterator.next()) {
-            IntRect absoluteChildDecendantBoundingBox;
-            computeCompositingRequirements(layer, curNode->layer(), overlapMap, childRecursionData, anyDescendantHas3DTransform, unclippedDescendants, absoluteChildDecendantBoundingBox);
-            absoluteDecendantBoundingBox.unite(absoluteChildDecendantBoundingBox);
-
-            // If we have to make a layer for this child, make one now so we can have a contents layer
-            // (since we need to ensure that the -ve z-order child renders underneath our contents).
-            if (childRecursionData.m_subtreeIsCompositing) {
-                reasonsToComposite |= CompositingReasonNegativeZIndexChildren;
-
-                if (!willBeCompositedOrSquashed) {
-                    // make layer compositing
-                    childRecursionData.m_compositingAncestor = layer;
-                    overlapMap.beginNewOverlapTestingContext();
-                    willBeCompositedOrSquashed = true;
-                    willHaveForegroundLayer = true;
-
-                    // FIXME: temporary solution for the first negative z-index composited child:
-                    //        re-compute the absBounds for the child so that we can add the
-                    //        negative z-index child's bounds to the new overlap context.
-                    overlapMap.beginNewOverlapTestingContext();
-                    overlapMap.add(curNode->layer(), curNode->layer()->ancestorDependentProperties().clippedAbsoluteBoundingBox);
-                    overlapMap.finishCurrentOverlapTestingContext();
-                }
-            }
-        }
-    }
-
-    if (willHaveForegroundLayer) {
-        ASSERT(willBeCompositedOrSquashed);
-        // A foreground layer effectively is a new backing for all subsequent children, so
-        // we don't need to test for overlap with anything behind this. So, we can finish
-        // the previous context that was accumulating rects for the negative z-index
-        // children, and start with a fresh new empty context.
-        overlapMap.finishCurrentOverlapTestingContext();
-        overlapMap.beginNewOverlapTestingContext();
-        // This layer is going to be composited, so children can safely ignore the fact that there's an
-        // animation running behind this layer, meaning they can rely on the overlap map testing again
-        childRecursionData.m_testingOverlap = true;
-    }
-
-    if (requiresCompositing(reasonsToComposite)) {
-        currentRecursionData.m_mostRecentCompositedLayer = layer;
-        childRecursionData.m_mostRecentCompositedLayer = layer;
-    }
-
-    RenderLayerStackingNodeIterator iterator(*layer->stackingNode(), NormalFlowChildren | PositiveZOrderChildren);
-    while (RenderLayerStackingNode* curNode = iterator.next()) {
-        IntRect absoluteChildDecendantBoundingBox;
-        computeCompositingRequirements(layer, curNode->layer(), overlapMap, childRecursionData, anyDescendantHas3DTransform, unclippedDescendants, absoluteChildDecendantBoundingBox);
-        absoluteDecendantBoundingBox.unite(absoluteChildDecendantBoundingBox);
-    }
-
-    currentRecursionData.m_mostRecentCompositedLayer = childRecursionData.m_mostRecentCompositedLayer;
-
-    // Now that the subtree has been traversed, we can check for compositing reasons that depended on the state of the subtree.
-
-    // If we entered compositing mode during the recursion, the root will also need to be composited (as long as accelerated compositing is enabled).
-    if (layer->isRootLayer()) {
-        if (inCompositingMode() && m_hasAcceleratedCompositing)
-            willBeCompositedOrSquashed = true;
-    }
-
-    // All layers (even ones that aren't being composited) need to get added to
-    // the overlap map. Layers that are not separately composited will paint into their
-    // compositing ancestor's backing, and so are still considered for overlap.
-    if (childRecursionData.m_compositingAncestor && !childRecursionData.m_compositingAncestor->isRootLayer())
-        overlapMap.add(layer, absBounds);
-
-    if (layer->stackingNode()->isStackingContext()) {
-        layer->setShouldIsolateCompositedDescendants(childRecursionData.m_hasUnisolatedCompositedBlendingDescendant);
-    } else {
-        layer->setShouldIsolateCompositedDescendants(false);
-        currentRecursionData.m_hasUnisolatedCompositedBlendingDescendant = childRecursionData.m_hasUnisolatedCompositedBlendingDescendant;
-    }
-
-    // Now check for reasons to become composited that depend on the state of descendant layers.
-    CompositingReasons subtreeCompositingReasons = subtreeReasonsForCompositing(layer->renderer(), childRecursionData.m_subtreeIsCompositing, anyDescendantHas3DTransform);
-    reasonsToComposite |= subtreeCompositingReasons;
-    if (!willBeCompositedOrSquashed && canBeComposited(layer) && requiresCompositingOrSquashing(subtreeCompositingReasons)) {
-        childRecursionData.m_compositingAncestor = layer;
-        // FIXME: this context push is effectively a no-op but needs to exist for
-        // now, because the code is designed to push overlap information to the
-        // second-from-top context of the stack.
-        overlapMap.beginNewOverlapTestingContext();
-        overlapMap.add(layer, absoluteDecendantBoundingBox);
-        willBeCompositedOrSquashed = true;
-    }
-
-    // If the original layer is composited, the reflection needs to be, too.
-    if (layer->reflectionInfo()) {
-        // FIXME: Shouldn't we call computeCompositingRequirements to handle a reflection overlapping with another renderer?
-        RenderLayer* reflectionLayer = layer->reflectionInfo()->reflectionLayer();
-        CompositingReasons reflectionCompositingReason = willBeCompositedOrSquashed ? CompositingReasonReflectionOfCompositedParent : CompositingReasonNone;
-        reflectionLayer->setCompositingReasons(reflectionLayer->compositingReasons() | reflectionCompositingReason);
-    }
-
-    // Subsequent layers in the parent's stacking context may also need to composite.
-    if (childRecursionData.m_subtreeIsCompositing)
-        currentRecursionData.m_subtreeIsCompositing = true;
-
-    if (willBeCompositedOrSquashed && layer->blendInfo().hasBlendMode())
-        currentRecursionData.m_hasUnisolatedCompositedBlendingDescendant = true;
-
-    // Set the flag to say that this SC has compositing children.
-    layer->setHasCompositingDescendant(childRecursionData.m_subtreeIsCompositing);
-
-    // Turn overlap testing off for later layers if it's already off, or if we have an animating transform.
-    // Note that if the layer clips its descendants, there's no reason to propagate the child animation to the parent layers. That's because
-    // we know for sure the animation is contained inside the clipping rectangle, which is already added to the overlap map.
-    bool isCompositedClippingLayer = canBeComposited(layer) && (reasonsToComposite & CompositingReasonClipsCompositingDescendants);
-    if ((!childRecursionData.m_testingOverlap && !isCompositedClippingLayer) || isRunningAcceleratedTransformAnimation(layer->renderer()))
-        currentRecursionData.m_testingOverlap = false;
-
-    if (childRecursionData.m_compositingAncestor == layer && !layer->isRootLayer())
-        overlapMap.finishCurrentOverlapTestingContext();
-
-    if (layer->isRootLayer()) {
-        // The root layer needs to be composited if anything else in the tree is composited.
-        // Otherwise, we can disable compositing entirely.
-        if (childRecursionData.m_subtreeIsCompositing || requiresCompositingOrSquashing(reasonsToComposite) || m_forceCompositingMode) {
-            willBeCompositedOrSquashed = true;
-            reasonsToComposite |= CompositingReasonRoot;
-        } else {
-            enableCompositingMode(false);
-            willBeCompositedOrSquashed = false;
-            reasonsToComposite = CompositingReasonNone;
-        }
-    }
-
-    if (requiresCompositing(reasonsToComposite))
-        currentRecursionData.m_mostRecentCompositedLayer = layer;
-
-    // At this point we have finished collecting all reasons to composite this layer.
-    layer->setCompositingReasons(reasonsToComposite);
-
-    descendantHas3DTransform |= anyDescendantHas3DTransform || layer->has3DTransform();
-}
-
 void RenderLayerCompositor::SquashingState::updateSquashingStateForNewMapping(CompositedLayerMappingPtr newCompositedLayerMapping, bool hasNewCompositedLayerMapping, LayoutPoint newOffsetFromAbsoluteForSquashingCLM)
 {
     // The most recent backing is done accumulating any more squashing layers.
@@ -1525,63 +1121,6 @@ bool RenderLayerCompositor::clipsCompositingDescendants(const RenderLayer* layer
     return layer->hasCompositingDescendant() && layer->renderer()->hasClipOrOverflowClip();
 }
 
-CompositingReasons RenderLayerCompositor::subtreeReasonsForCompositing(RenderObject* renderer, bool hasCompositedDescendants, bool has3DTransformedDescendants) const
-{
-    CompositingReasons subtreeReasons = CompositingReasonNone;
-
-    // FIXME: this seems to be a potentially different layer than the layer for which this was called. May not be an error, but is very confusing.
-    RenderLayer* layer = toRenderBoxModelObject(renderer)->layer();
-
-    // When a layer has composited descendants, some effects, like 2d transforms, filters, masks etc must be implemented
-    // via compositing so that they also apply to those composited descdendants.
-    if (hasCompositedDescendants) {
-        if (layer->transform())
-            subtreeReasons |= CompositingReasonTransformWithCompositedDescendants;
-
-        if (layer->shouldIsolateCompositedDescendants()) {
-            ASSERT(layer->stackingNode()->isStackingContext());
-            subtreeReasons |= CompositingReasonIsolateCompositedDescendants;
-        }
-
-        // If the implementation of createsGroup changes, we need to be aware of that in this part of code.
-        ASSERT((renderer->isTransparent() || renderer->hasMask() || renderer->hasFilter() || renderer->hasBlendMode()) == renderer->createsGroup());
-        if (renderer->isTransparent())
-            subtreeReasons |= CompositingReasonOpacityWithCompositedDescendants;
-        if (renderer->hasMask())
-            subtreeReasons |= CompositingReasonMaskWithCompositedDescendants;
-        if (renderer->hasFilter())
-            subtreeReasons |= CompositingReasonFilterWithCompositedDescendants;
-        if (renderer->hasBlendMode())
-            subtreeReasons |= CompositingReasonBlendingWithCompositedDescendants;
-
-        if (renderer->hasReflection())
-            subtreeReasons |= CompositingReasonReflectionWithCompositedDescendants;
-
-        if (renderer->hasClipOrOverflowClip())
-            subtreeReasons |= CompositingReasonClipsCompositingDescendants;
-    }
-
-
-    // A layer with preserve-3d or perspective only needs to be composited if there are descendant layers that
-    // will be affected by the preserve-3d or perspective.
-    if (has3DTransformedDescendants) {
-        if (renderer->style()->transformStyle3D() == TransformStyle3DPreserve3D)
-            subtreeReasons |= CompositingReasonPreserve3DWith3DDescendants;
-
-        if (renderer->style()->hasPerspective())
-            subtreeReasons |= CompositingReasonPerspectiveWith3DDescendants;
-    }
-
-    return subtreeReasons;
-}
-
-bool RenderLayerCompositor::isRunningAcceleratedTransformAnimation(RenderObject* renderer) const
-{
-    if (!m_compositingReasonFinder.hasAnimationTrigger())
-        return false;
-    return renderer->style()->hasCurrentTransformAnimation();
-}
-
 // If an element has negative z-index children, those children render in front of the
 // layer background, so we need an extra 'contents' layer for the foreground of the layer
 // object.