Reland main thread position sticky implementation.

third_party/WebKit/Source/core/layout/compositing/CompositingInputsUpdater.cpp

 // 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 "core/layout/compositing/CompositingInputsUpdater.h"
 
+#include "core/frame/FrameView.h"
 #include "core/layout/LayoutBlock.h"
+#include "core/layout/LayoutView.h"
 #include "core/layout/compositing/CompositedLayerMapping.h"
 #include "core/layout/compositing/PaintLayerCompositor.h"
 #include "core/paint/PaintLayer.h"
 #include "platform/TraceEvent.h"
 
 namespace blink {
 
 CompositingInputsUpdater::CompositingInputsUpdater(PaintLayer* rootLayer)
     : m_geometryMap(UseTransforms)
     , m_rootLayer(rootLayer)
@@ skipping 72 matching lines @@
         }
     }
     return false;
 }
 
 void CompositingInputsUpdater::updateRecursive(PaintLayer* layer, UpdateType updateType, AncestorInfo info)
 {
     if (!layer->childNeedsCompositingInputsUpdate() && updateType != ForceUpdate)
         return;
 
+    const PaintLayer* previousOverflowLayer = layer->ancestorOverflowLayer();
+    layer->updateAncestorOverflowLayer(info.lastOverflowClipLayer);
+    if (info.lastOverflowClipLayer && layer->needsCompositingInputsUpdate() && layer->layoutObject()->style()->position() == StickyPosition) {
+        if (info.lastOverflowClipLayer != previousOverflowLayer) {
+            // Old ancestor scroller should no longer have these constraints.
+            ASSERT(!previousOverflowLayer || !previousOverflowLayer->getScrollableArea()->stickyConstraintsMap().contains(layer));
+
+            if (info.lastOverflowClipLayer->isRootLayer())
+                layer->layoutObject()->view()->frameView()->addViewportConstrainedObject(layer->layoutObject());
+            else if (previousOverflowLayer && previousOverflowLayer->isRootLayer())
+                layer->layoutObject()->view()->frameView()->removeViewportConstrainedObject(layer->layoutObject());
+        }
+        layer->layoutObject()->updateStickyPositionConstraints();
+
+        // Sticky position constraints and ancestor overflow scroller affect
+        // the sticky layer position, so we need to update it again here.
+        // TODO(flackr): This should be refactored in the future to be clearer
+        // (i.e. update layer position and ancestor inputs updates in the
+        // same walk)
+        layer->updateLayerPosition();
+    }
+
     m_geometryMap.pushMappingsToAncestor(layer, layer->parent());
 
     if (layer->hasCompositedLayerMapping())
         info.enclosingCompositedLayer = layer;
 
     if (layer->needsCompositingInputsUpdate()) {
         if (info.enclosingCompositedLayer)
             info.enclosingCompositedLayer->compositedLayerMapping()->setNeedsGraphicsLayerUpdate(GraphicsLayerUpdateSubtree);
         updateType = ForceUpdate;
     }
@@ skipping 46 matching lines @@
                     rareProperties.scrollParent = rareProperties.ancestorScrollingLayer;
             }
         }
 
         layer->updateAncestorDependentCompositingInputs(properties, rareProperties, info.hasAncestorWithClipPath);
     }
 
     if (layer->stackingNode()->isStackingContext())
         info.ancestorStackingContext = layer;
 
+    if (layer->isRootLayer() || layer->layoutObject()->hasOverflowClip())
+        info.lastOverflowClipLayer = layer;
+
     if (layer->scrollsOverflow())
         info.lastScrollingAncestor = layer;
 
     if (layer->layoutObject()->hasClipRelatedProperty())
         info.hasAncestorWithClipRelatedProperty = true;
 
     if (layer->layoutObject()->hasClipPath())
         info.hasAncestorWithClipPath = true;
 
     bool hasDescendantWithClipPath = false;
@@ skipping 18 matching lines @@
     ASSERT(!layer->childNeedsCompositingInputsUpdate());
     ASSERT(!layer->needsCompositingInputsUpdate());
 
     for (PaintLayer* child = layer->firstChild(); child; child = child->nextSibling())
         assertNeedsCompositingInputsUpdateBitsCleared(child);
 }
 
 #endif
 
 } // namespace blink