Delete the Layer Squashing runtime feature.

Source/core/rendering/compositing/CompositingLayerAssigner.cpp

 /*
  * Copyright (C) 2009, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2014 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 21 matching lines @@
 #include "platform/TraceEvent.h"
 
 namespace blink {
 
 // We will only allow squashing if the bbox-area:squashed-area doesn't exceed
 // the ratio |gSquashingSparsityTolerance|:1.
 static uint64_t gSquashingSparsityTolerance = 6;
 
 CompositingLayerAssigner::CompositingLayerAssigner(RenderLayerCompositor* compositor)
     : m_compositor(compositor)
-    , m_layerSquashingEnabled(compositor->layerSquashingEnabled())
     , m_layersChanged(false)
 {
 }
 
 CompositingLayerAssigner::~CompositingLayerAssigner()
 {
 }
 
 void CompositingLayerAssigner::assign(RenderLayer* updateRoot, Vector<RenderLayer*>& layersNeedingPaintInvalidation)
 {
@@ skipping 26 matching lines @@
     const uint64_t newBoundingRectArea = newBoundingRect.size().area();
     const uint64_t newSquashedArea = squashingState.totalAreaOfSquashedRects + bounds.size().area();
     return newBoundingRectArea > gSquashingSparsityTolerance * newSquashedArea;
 }
 
 bool CompositingLayerAssigner::needsOwnBacking(const RenderLayer* layer) const
 {
     if (!m_compositor->canBeComposited(layer))
         return false;
 
-    // If squashing is disabled, then layers that would have been squashed should just be separately composited.
-    bool needsOwnBackingForDisabledSquashing = !m_layerSquashingEnabled && requiresSquashing(layer->compositingReasons());
-
-    return requiresCompositing(layer->compositingReasons()) || needsOwnBackingForDisabledSquashing || (m_compositor->staleInCompositingMode() && layer->isRootLayer());
+    return requiresCompositing(layer->compositingReasons()) || (m_compositor->staleInCompositingMode() && layer->isRootLayer());
 }
 
 CompositingStateTransitionType CompositingLayerAssigner::computeCompositedLayerUpdate(RenderLayer* layer)
 {
     CompositingStateTransitionType update = NoCompositingStateChange;
     if (needsOwnBacking(layer)) {
         if (!layer->hasCompositedLayerMapping()) {
             update = AllocateOwnCompositedLayerMapping;
         }
     } else {
         if (layer->hasCompositedLayerMapping())
             update = RemoveOwnCompositedLayerMapping;
 
-        if (m_layerSquashingEnabled) {
-            if (!layer->subtreeIsInvisible() && requiresSquashing(layer->compositingReasons())) {
-                // We can't compute at this time whether the squashing layer update is a no-op,
-                // since that requires walking the render layer tree.
-                update = PutInSquashingLayer;
-            } else if (layer->groupedMapping() || layer->lostGroupedMapping()) {
-                update = RemoveFromSquashingLayer;
-            }
+        if (!layer->subtreeIsInvisible() && requiresSquashing(layer->compositingReasons())) {
+            // We can't compute at this time whether the squashing layer update is a no-op,
+            // since that requires walking the render layer tree.
+            update = PutInSquashingLayer;
+        } else if (layer->groupedMapping() || layer->lostGroupedMapping()) {
+            update = RemoveFromSquashingLayer;
         }
     }
     return update;
 }
 
 CompositingReasons CompositingLayerAssigner::getReasonsPreventingSquashing(const RenderLayer* layer, const CompositingLayerAssigner::SquashingState& squashingState)
 {
     if (!squashingState.haveAssignedBackingsToEntireSquashingLayerSubtree)
         return CompositingReasonSquashingWouldBreakPaintOrder;
 
@@ skipping 106 matching lines @@
     }
     m_compositor->updateDirectCompositingReasons(reflectionLayer);
 
     // FIXME: Why do we updateGraphicsLayerConfiguration here instead of in the GraphicsLayerUpdater?
     if (reflectionLayer->hasCompositedLayerMapping())
         reflectionLayer->compositedLayerMapping()->updateGraphicsLayerConfiguration();
 }
 
 void CompositingLayerAssigner::assignLayersToBackingsInternal(RenderLayer* layer, SquashingState& squashingState, Vector<RenderLayer*>& layersNeedingPaintInvalidation)
 {
-    if (m_layerSquashingEnabled && requiresSquashing(layer->compositingReasons())) {
+    if (requiresSquashing(layer->compositingReasons())) {
         CompositingReasons reasonsPreventingSquashing = getReasonsPreventingSquashing(layer, squashingState);
         if (reasonsPreventingSquashing)
             layer->setCompositingReasons(layer->compositingReasons() | reasonsPreventingSquashing);
     }
 
     CompositingStateTransitionType compositedLayerUpdate = computeCompositedLayerUpdate(layer);
 
     if (m_compositor->allocateOrClearCompositedLayerMapping(layer, compositedLayerUpdate)) {
         TRACE_LAYER_INVALIDATION(layer, InspectorLayerInvalidationTrackingEvent::NewCompositedLayer);
         layersNeedingPaintInvalidation.append(layer);
         m_layersChanged = true;
     }
 
     // FIXME: special-casing reflection layers here is not right.
     if (layer->reflectionInfo())
         assignLayersToBackingsForReflectionLayer(layer->reflectionInfo()->reflectionLayer(), layersNeedingPaintInvalidation);
 
     // Add this layer to a squashing backing if needed.
-    if (m_layerSquashingEnabled) {
-        updateSquashingAssignment(layer, squashingState, compositedLayerUpdate, layersNeedingPaintInvalidation);
+    updateSquashingAssignment(layer, squashingState, compositedLayerUpdate, layersNeedingPaintInvalidation);
 
-        const bool layerIsSquashed = compositedLayerUpdate == PutInSquashingLayer || (compositedLayerUpdate == NoCompositingStateChange && layer->groupedMapping());
-        if (layerIsSquashed) {
-            squashingState.nextSquashedLayerIndex++;
-            IntRect layerBounds = layer->clippedAbsoluteBoundingBox();
-            squashingState.totalAreaOfSquashedRects += layerBounds.size().area();
-            squashingState.boundingRect.unite(layerBounds);
-        }
+    const bool layerIsSquashed = compositedLayerUpdate == PutInSquashingLayer || (compositedLayerUpdate == NoCompositingStateChange && layer->groupedMapping());
+    if (layerIsSquashed) {
+        squashingState.nextSquashedLayerIndex++;
+        IntRect layerBounds = layer->clippedAbsoluteBoundingBox();
+        squashingState.totalAreaOfSquashedRects += layerBounds.size().area();
+        squashingState.boundingRect.unite(layerBounds);
     }
 
     if (layer->stackingNode()->isStackingContext()) {
         RenderLayerStackingNodeIterator iterator(*layer->stackingNode(), NegativeZOrderChildren);
         while (RenderLayerStackingNode* curNode = iterator.next())
             assignLayersToBackingsInternal(curNode->layer(), squashingState, layersNeedingPaintInvalidation);
     }
 
-    if (m_layerSquashingEnabled) {
-        // At this point, if the layer is to be separately composited, then its backing becomes the most recent in paint-order.
-        if (layer->compositingState() == PaintsIntoOwnBacking) {
-            ASSERT(!requiresSquashing(layer->compositingReasons()));
-            squashingState.updateSquashingStateForNewMapping(layer->compositedLayerMapping(), layer->hasCompositedLayerMapping());
-        }
+    // At this point, if the layer is to be separately composited, then its backing becomes the most recent in paint-order.
+    if (layer->compositingState() == PaintsIntoOwnBacking) {
+        ASSERT(!requiresSquashing(layer->compositingReasons()));
+        squashingState.updateSquashingStateForNewMapping(layer->compositedLayerMapping(), layer->hasCompositedLayerMapping());
     }
 
     if (layer->scrollParent())
         layer->scrollParent()->scrollableArea()->setTopmostScrollChild(layer);
 
     if (layer->needsCompositedScrolling())
         layer->scrollableArea()->setTopmostScrollChild(0);
 
     RenderLayerStackingNodeIterator iterator(*layer->stackingNode(), NormalFlowChildren | PositiveZOrderChildren);
     while (RenderLayerStackingNode* curNode = iterator.next())
         assignLayersToBackingsInternal(curNode->layer(), squashingState, layersNeedingPaintInvalidation);
 
     if (squashingState.hasMostRecentMapping && &squashingState.mostRecentMapping->owningLayer() == layer)
         squashingState.haveAssignedBackingsToEntireSquashingLayerSubtree = true;
 }
 
 }