Add PaintPropertyTreeBuildContext force_subtree_update categories.

This patch changes force_subtree_update bool into "reasons" that fall
into one of two categories:
  - Isolation piercing, meaning that the update crosses and recurses
    into an isolation boundary.
  - Isolation blocking, meaning that the recursion may be blocked by
    isolation.

R=chrishtr@chromium.org, pdr@chromium.org, wangxianzhu@chromium.org

Cq-Include-Trybots: luci.chromium.try:linux_layout_tests_slimming_paint_v2;master.tryserver.blink:linux_trusty_blink_rel
Change-Id: Ie5389a02b8cc529ca93bf0e50b225b0f343e2439
Reviewed-on: https://chromium-review.googlesource.com/1247201Reviewed-by: Philip Rogers <pdr@chromium.org>
Reviewed-by: Xianzhu Wang <wangxianzhu@chromium.org>
Commit-Queue: vmpstr <vmpstr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#594760}

third_party/blink/renderer/core/paint/paint_property_tree_builder.cc

@@ -44,6 +44,22 @@
 
 namespace blink {
 
+namespace {
+
+bool AreSubtreeUpdateReasonsIsolationPiercing(unsigned reasons) {
+  // This is written to mean that if we have any reason other than the specified
+  // ones then the reasons are isolation piercing. This means that if new
+  // reasons are added, they will be isolation piercing by default.
+  //  - Isolation establishes a containing block for all descendants, so it is
+  //    not piercing.
+  // TODO(vmpstr): Investigate if transform style is also isolated.
+  return reasons &
+         ~(static_cast<unsigned>(
+             SubtreePaintPropertyUpdateReason::kContainerChainMayChange));
+}
+
+}  // namespace
+
 PaintPropertyTreeBuilderFragmentContext::
     PaintPropertyTreeBuilderFragmentContext()
     : current_effect(&EffectPaintPropertyNode::Root()) {
@@ -55,6 +71,13 @@ PaintPropertyTreeBuilderFragmentContext::
       &ScrollPaintPropertyNode::Root();
 }
 
+PaintPropertyTreeBuilderContext::PaintPropertyTreeBuilderContext()
+    : force_subtree_update_reasons(0u),
+      clip_changed(false),
+      is_repeating_fixed_position(false),
+      has_svg_hidden_container_ancestor(false),
+      supports_composited_raster_invalidation(true) {}
+
 void VisualViewportPaintPropertyTreeBuilder::Update(
     VisualViewport& visual_viewport,
     PaintPropertyTreeBuilderContext& full_context) {
@@ -112,7 +135,11 @@ class FragmentPaintPropertyTreeBuilder {
         properties_(fragment_data.PaintProperties()) {}
 
   ~FragmentPaintPropertyTreeBuilder() {
-    full_context_.force_subtree_update |= property_added_or_removed_;
+    if (property_added_or_removed_) {
+      // Tree topology changes are blocked by isolation.
+      full_context_.force_subtree_update_reasons |=
+          PaintPropertyTreeBuilderContext::kSubtreeUpdateIsolationBlocked;
+    }
 #if DCHECK_IS_ON()
     if (properties_)
       PaintPropertyTreePrinter::UpdateDebugNames(object_, *properties_);
@@ -159,7 +186,7 @@ class FragmentPaintPropertyTreeBuilder {
 
   bool NeedsPaintPropertyUpdate() const {
     return object_.NeedsPaintPropertyUpdate() ||
-           full_context_.force_subtree_update;
+           full_context_.force_subtree_update_reasons;
   }
 
   void OnUpdate(const ObjectPaintProperties::UpdateResult& result) {
@@ -1263,7 +1290,7 @@ void FragmentPaintPropertyTreeBuilder::UpdateOverflowControlsClip() {
     properties_->ClearOverflowControlsClip();
   }
 
-  // No need to set force_subtree_update and clip_changed because
+  // No need to set force_subtree_update_reasons and clip_changed because
   // OverflowControlsClip applies to overflow controls only, not descendants.
   // We also don't walk into custom scrollbars in PrePaintTreeWalk and
   // LayoutObjects under custom scrollbars don't support paint properties.
@@ -1550,8 +1577,11 @@ void FragmentPaintPropertyTreeBuilder::UpdateScrollAndScrollTranslation() {
       // so ensure the entire subtree is updated when reasons change.
       if (auto* existing_scroll = properties_->Scroll()) {
         if (existing_scroll->GetMainThreadScrollingReasons() !=
-            state.main_thread_scrolling_reasons)
-          full_context_.force_subtree_update = true;
+            state.main_thread_scrolling_reasons) {
+          // Main thread scrolling reasons cross into isolation.
+          full_context_.force_subtree_update_reasons |=
+              PaintPropertyTreeBuilderContext::kSubtreeUpdateIsolationPiercing;
+        }
       }
 
       if (RuntimeEnabledFeatures::SlimmingPaintV2Enabled() ||
@@ -2042,7 +2072,9 @@ void FragmentPaintPropertyTreeBuilder::UpdateForObjectLocationAndSize(
   if (fragment_data_.PaintOffset() != context_.current.paint_offset) {
     // Many paint properties depend on paint offset so we force an update of
     // the entire subtree on paint offset changes.
-    full_context_.force_subtree_update = true;
+    // However, they are blocked by isolation.
+    full_context_.force_subtree_update_reasons |=
+        PaintPropertyTreeBuilderContext::kSubtreeUpdateIsolationBlocked;
 
     object_.GetMutableForPainting().SetShouldCheckForPaintInvalidation();
     fragment_data_.SetPaintOffset(context_.current.paint_offset);
@@ -2100,7 +2132,7 @@ void FragmentPaintPropertyTreeBuilder::UpdateForSelf() {
 
 #if DCHECK_IS_ON()
   FindObjectPropertiesNeedingUpdateScope check_needs_update_scope(
-      object_, fragment_data_, full_context_.force_subtree_update);
+      object_, fragment_data_, full_context_.force_subtree_update_reasons);
 #endif
 
   if (properties_) {
@@ -2120,7 +2152,7 @@ void FragmentPaintPropertyTreeBuilder::UpdateForSelf() {
 void FragmentPaintPropertyTreeBuilder::UpdateForChildren() {
 #if DCHECK_IS_ON()
   FindObjectPropertiesNeedingUpdateScope check_needs_update_scope(
-      object_, fragment_data_, full_context_.force_subtree_update);
+      object_, fragment_data_, full_context_.force_subtree_update_reasons);
 #endif
 
   if (properties_) {
@@ -2151,7 +2183,9 @@ void PaintPropertyTreeBuilder::InitFragmentPaintProperties(
   if (needs_paint_properties) {
     fragment.EnsurePaintProperties();
   } else if (fragment.PaintProperties()) {
-    context_.force_subtree_update = true;
+    // Tree topology changes are blocked by isolation.
+    context_.force_subtree_update_reasons |=
+        PaintPropertyTreeBuilderContext::kSubtreeUpdateIsolationBlocked;
     fragment.ClearPaintProperties();
   }
   fragment.SetPaginationOffset(pagination_offset);
@@ -2906,7 +2940,14 @@ bool PaintPropertyTreeBuilder::UpdateForChildren() {
   // means it can clear that reason and possibly skip the subtree update.
   if (object_.SubtreePaintPropertyUpdateReasons() !=
       static_cast<unsigned>(SubtreePaintPropertyUpdateReason::kNone)) {
-    context_.force_subtree_update = true;
+    if (AreSubtreeUpdateReasonsIsolationPiercing(
+            object_.SubtreePaintPropertyUpdateReasons())) {
+      context_.force_subtree_update_reasons |=
+          PaintPropertyTreeBuilderContext::kSubtreeUpdateIsolationPiercing;
+    } else {
+      context_.force_subtree_update_reasons |=
+          PaintPropertyTreeBuilderContext::kSubtreeUpdateIsolationBlocked;
+    }
   }
   if (object_.CanContainAbsolutePositionObjects())
     context_.container_for_absolute_position = &object_;

third_party/blink/renderer/core/paint/paint_property_tree_builder.h

@@ -115,23 +115,15 @@ struct PaintPropertyTreeBuilderContext {
   DISALLOW_NEW();
 
  public:
-  PaintPropertyTreeBuilderContext() = default;
+  PaintPropertyTreeBuilderContext();
 
   Vector<PaintPropertyTreeBuilderFragmentContext, 1> fragments;
   const LayoutObject* container_for_absolute_position = nullptr;
   const LayoutObject* container_for_fixed_position = nullptr;
 
-  // True if a change has forced all properties in a subtree to be updated. This
-  // can be set due to paint offset changes or when the structure of the
-  // property tree changes (i.e., a node is added or removed).
-  bool force_subtree_update = false;
-
-  // Whether a clip paint property node appeared, disappeared, or changed
-  // its clip since this variable was last set to false. This is used
-  // to find out whether a clip changed since the last transform update.
-  // Code outside of this class resets clip_changed to false when transforms
-  // change.
-  bool clip_changed = false;
+  // The physical bounding box of all appearances of the repeating table section
+  // in the flow thread or the paged LayoutView.
+  LayoutRect repeating_table_section_bounding_box;
 
 #if DCHECK_IS_ON()
   // When DCHECK_IS_ON() we create PaintPropertyTreeBuilderContext even if not
@@ -146,21 +138,43 @@ struct PaintPropertyTreeBuilderContext {
   // fragment where the object first appears.
   const LayoutTableSection* repeating_table_section = nullptr;
 
+  // Specifies the reason the subtree update was forced. For simplicity, this
+  // only categorizes it into two categories:
+  // - Isolation piercing, meaning that the update is required for subtrees
+  //   under an isolation boundary.
+  // - Isolation blocked, meaning that the recursion can be blocked by
+  //   isolation.
+  enum SubtreeUpdateReason : unsigned {
+    kSubtreeUpdateIsolationPiercing = 1 << 0,
+    kSubtreeUpdateIsolationBlocked = 1 << 1
+  };
+
+  // True if a change has forced all properties in a subtree to be updated. This
+  // can be set due to paint offset changes or when the structure of the
+  // property tree changes (i.e., a node is added or removed).
+  unsigned force_subtree_update_reasons : 2;
+
+  // Note that the next four bitfields are conceptually bool, but are declared
+  // as unsigned in order to be packed in the same word as the above bitfield.
+
+  // Whether a clip paint property node appeared, disappeared, or changed
+  // its clip since this variable was last set to false. This is used
+  // to find out whether a clip changed since the last transform update.
+  // Code outside of this class resets clip_changed to false when transforms
+  // change.
+  unsigned clip_changed : 1;
+
   // When printing, fixed-position objects and their descendants need to repeat
   // in each page.
-  bool is_repeating_fixed_position = false;
+  unsigned is_repeating_fixed_position : 1;
 
   // True if the current subtree is underneath a LayoutSVGHiddenContainer
   // ancestor.
-  bool has_svg_hidden_container_ancestor = false;
-
-  // The physical bounding box of all appearances of the repeating table section
-  // in the flow thread or the paged LayoutView.
-  LayoutRect repeating_table_section_bounding_box;
+  unsigned has_svg_hidden_container_ancestor : 1;
 
   // Whether composited raster invalidation is supported for this object.
   // If not, subtree invalidations occur on every property tree change.
-  bool supports_composited_raster_invalidation = true;
+  unsigned supports_composited_raster_invalidation : 1;
 };
 
 class VisualViewportPaintPropertyTreeBuilder {

third_party/blink/renderer/core/paint/pre_paint_tree_walk.cc

@@ -282,7 +282,7 @@ bool PrePaintTreeWalk::NeedsTreeBuilderContextUpdate(
     const LayoutObject& object,
     const PrePaintTreeWalkContext& parent_context) {
   if (parent_context.tree_builder_context &&
-      parent_context.tree_builder_context->force_subtree_update) {
+      parent_context.tree_builder_context->force_subtree_update_reasons) {
     return true;
   }
   // The following CHECKs are for debugging crbug.com/816810.