Reland of Skip paint property update and visual rect update if no geometry change

third_party/WebKit/Source/core/paint/PrePaintTreeWalk.cpp

Index: third_party/WebKit/Source/core/paint/PrePaintTreeWalk.cpp
diff --git a/third_party/WebKit/Source/core/paint/PrePaintTreeWalk.cpp b/third_party/WebKit/Source/core/paint/PrePaintTreeWalk.cpp
index eca81e847a11fdab77a40a570d0fe25197748e85..6715959df4a1d838404810a8a61a82fefffe728d 100644
--- a/third_party/WebKit/Source/core/paint/PrePaintTreeWalk.cpp
+++ b/third_party/WebKit/Source/core/paint/PrePaintTreeWalk.cpp
@@ -19,17 +19,28 @@ struct PrePaintTreeWalkContext {
   PrePaintTreeWalkContext()
       : treeBuilderContext(
             WTF::wrapUnique(new PaintPropertyTreeBuilderContext)),
-        paintInvalidatorContext(*treeBuilderContext),
+        paintInvalidatorContext(treeBuilderContext.get()),
         ancestorOverflowPaintLayer(nullptr),
         ancestorTransformedOrRootPaintLayer(nullptr) {}
-  PrePaintTreeWalkContext(const PrePaintTreeWalkContext& parentContext)
-      : treeBuilderContext(WTF::wrapUnique(new PaintPropertyTreeBuilderContext(
-            *parentContext.treeBuilderContext))),
-        paintInvalidatorContext(*treeBuilderContext,
+
+  PrePaintTreeWalkContext(const PrePaintTreeWalkContext& parentContext,
+                          bool needsTreeBuilderContext)
+      : treeBuilderContext(
+            WTF::wrapUnique(needsTreeBuilderContext || DCHECK_IS_ON()
+                                ? new PaintPropertyTreeBuilderContext(
+                                      *parentContext.treeBuilderContext)
+                                : nullptr)),
+        paintInvalidatorContext(treeBuilderContext.get(),
                                 parentContext.paintInvalidatorContext),
         ancestorOverflowPaintLayer(parentContext.ancestorOverflowPaintLayer),
         ancestorTransformedOrRootPaintLayer(
-            parentContext.ancestorTransformedOrRootPaintLayer) {}
+            parentContext.ancestorTransformedOrRootPaintLayer) {
+#if DCHECK_IS_ON()
+    if (needsTreeBuilderContext)
+      DCHECK(parentContext.treeBuilderContext->isActuallyNeeded);
+    treeBuilderContext->isActuallyNeeded = needsTreeBuilderContext;
+#endif
+  }
 
   // PaintPropertyTreeBuilderContext is large and can lead to stack overflows
   // when recursion is deep so this context object is allocated on the heap.
@@ -53,10 +64,8 @@ void PrePaintTreeWalk::walk(FrameView& rootFrame) {
   initialContext.ancestorTransformedOrRootPaintLayer =
       rootFrame.layoutView()->layer();
 
-  // GeometryMapper caches depend on paint properties.
-  if (rootFrame.needsPaintPropertyUpdate() ||
-      (rootFrame.layoutView() &&
-       !shouldEndWalkBefore(*rootFrame.layoutView(), initialContext)))
+  // GeometryMapper depends on paint properties.
+  if (needsTreeBuilderContextUpdate(rootFrame, initialContext))
     GeometryMapper::clearCache();
 
   walk(rootFrame, initialContext);
@@ -70,11 +79,15 @@ void PrePaintTreeWalk::walk(FrameView& frameView,
     return;
   }
 
-  PrePaintTreeWalkContext context(parentContext);
+  bool needsTreeBuilderContextUpdate =
+      this->needsTreeBuilderContextUpdate(frameView, parentContext);
+  PrePaintTreeWalkContext context(parentContext, needsTreeBuilderContextUpdate);
   // ancestorOverflowLayer does not cross frame boundaries.
   context.ancestorOverflowPaintLayer = nullptr;
-  m_propertyTreeBuilder.updateProperties(frameView,
-                                         *context.treeBuilderContext);
+  if (context.treeBuilderContext) {
+    m_propertyTreeBuilder.updateProperties(frameView,
+                                           *context.treeBuilderContext);
+  }
   m_paintInvalidator.invalidatePaintIfNeeded(frameView,
                                              context.paintInvalidatorContext);
 
@@ -204,41 +217,61 @@ void PrePaintTreeWalk::invalidatePaintLayerOptimizationsIfNeeded(
     // All subsequences which are contained below this paintLayer must also
     // be checked.
     context.paintInvalidatorContext.forcedSubtreeInvalidationFlags |=
-        PaintInvalidatorContext::ForcedSubtreeInvalidationRectUpdate;
+        PaintInvalidatorContext::ForcedSubtreeVisualRectUpdate;
   }
 
   paintLayer.setPreviousPaintingClipRects(*clipRects);
 }
 
-bool PrePaintTreeWalk::shouldEndWalkBefore(
-    const LayoutObject& object,
+bool PrePaintTreeWalk::needsTreeBuilderContextUpdate(
+    const FrameView& frameView,
     const PrePaintTreeWalkContext& context) {
-  return !object.needsPaintPropertyUpdate() &&
-         !object.descendantNeedsPaintPropertyUpdate() &&
-         !context.treeBuilderContext->forceSubtreeUpdate &&
-         !context.paintInvalidatorContext.forcedSubtreeInvalidationFlags &&
-         !object.shouldCheckForPaintInvalidation();
+  return frameView.needsPaintPropertyUpdate() ||
+         (frameView.layoutView() &&
+          needsTreeBuilderContextUpdate(*frameView.layoutView(), context));
+}
+
+bool PrePaintTreeWalk::needsTreeBuilderContextUpdate(
+    const LayoutObject& object,
+    const PrePaintTreeWalkContext& parentContext) {
+  return object.needsPaintPropertyUpdate() ||
+         object.descendantNeedsPaintPropertyUpdate() ||
+         (parentContext.treeBuilderContext &&
+          parentContext.treeBuilderContext->forceSubtreeUpdate) ||
+         // If the object needs visual rect update, we should update tree
+         // builder context which is needed by visual rect update.
+         parentContext.paintInvalidatorContext.needsVisualRectUpdate(object);
 }
 
 void PrePaintTreeWalk::walk(const LayoutObject& object,
                             const PrePaintTreeWalkContext& parentContext) {
-  if (shouldEndWalkBefore(object, parentContext))
+  // Early out from the tree walk if possible.
+  bool needsTreeBuilderContextUpdate =
+      this->needsTreeBuilderContextUpdate(object, parentContext);
+  if (!needsTreeBuilderContextUpdate &&
+      !object.shouldCheckForPaintInvalidation())
     return;
 
-  PrePaintTreeWalkContext context(parentContext);
+  PrePaintTreeWalkContext context(parentContext, needsTreeBuilderContextUpdate);
 
   // This must happen before updatePropertiesForSelf, because the latter reads
   // some of the state computed here.
   updateAuxiliaryObjectProperties(object, context);
 
-  m_propertyTreeBuilder.updatePropertiesForSelf(object,
-                                                *context.treeBuilderContext);
+  if (context.treeBuilderContext) {
+    DCHECK(context.treeBuilderContext);
+    m_propertyTreeBuilder.updatePropertiesForSelf(object,
+                                                  *context.treeBuilderContext);
+  }
+
   m_paintInvalidator.invalidatePaintIfNeeded(object,
                                              context.paintInvalidatorContext);
-  m_propertyTreeBuilder.updatePropertiesForChildren(
-      object, *context.treeBuilderContext);
 
-  invalidatePaintLayerOptimizationsIfNeeded(object, context);
+  if (context.treeBuilderContext) {
+    m_propertyTreeBuilder.updatePropertiesForChildren(
+        object, *context.treeBuilderContext);
+    invalidatePaintLayerOptimizationsIfNeeded(object, context);
+  }
 
   for (const LayoutObject* child = object.slowFirstChild(); child;
        child = child->nextSibling()) {
@@ -253,11 +286,13 @@ void PrePaintTreeWalk::walk(const LayoutObject& object,
     const LayoutPart& layoutPart = toLayoutPart(object);
     FrameViewBase* frameViewBase = layoutPart.frameViewBase();
     if (frameViewBase && frameViewBase->isFrameView()) {
-      context.treeBuilderContext->current.paintOffset +=
-          layoutPart.replacedContentRect().location() -
-          frameViewBase->frameRect().location();
-      context.treeBuilderContext->current.paintOffset =
-          roundedIntPoint(context.treeBuilderContext->current.paintOffset);
+      if (context.treeBuilderContext) {
+        context.treeBuilderContext->current.paintOffset +=
+            layoutPart.replacedContentRect().location() -
+            frameViewBase->frameRect().location();
+        context.treeBuilderContext->current.paintOffset =
+            roundedIntPoint(context.treeBuilderContext->current.paintOffset);
+      }
       walk(*toFrameView(frameViewBase), context);
     }
     // TODO(pdr): Investigate RemoteFrameView (crbug.com/579281).