[layoutng] Re-introduce optimization

This implements a previously skipped optimization in a different
way for flexbox with NG children.

Adding css3/flexbox/bug646288.html to expectations because it seems like
that passed by accident; it does not use percentages.

Bug: 839661

Cq-Include-Trybots: master.tryserver.chromium.linux:linux_layout_tests_layout_ng
Change-Id: I910b18f24d9d7a27d25f2d9bbd00bc585a3c5516
Reviewed-on: https://chromium-review.googlesource.com/1051005
Commit-Queue: Christian Biesinger <cbiesinger@chromium.org>
Reviewed-by: Emil A Eklund <eae@chromium.org>
Reviewed-by: Morten Stenshorne <mstensho@chromium.org>
Cr-Commit-Position: refs/heads/master@{#557353}

third_party/WebKit/LayoutTests/FlagExpectations/enable-blink-features=LayoutNG

@@ -157,6 +157,7 @@ crbug.com/591099 css3/filters/effect-brightness-clamping.html [ Failure ]
 crbug.com/591099 css3/filters/effect-brightness.html [ Failure ]
 crbug.com/714962 css3/filters/effect-reference-zoom-hw.html [ Failure ]
 crbug.com/591099 css3/filters/multiple-references-id-mutate-crash-2.html [ Crash ]
+crbug.com/591099 css3/flexbox/bug646288.html [ Failure ]
 crbug.com/591099 css3/flexbox/bug669714.html [ Failure ]
 crbug.com/591099 css3/flexbox/flex-flow-border.html [ Failure ]
 crbug.com/591099 css3/flexbox/flex-flow-margins-auto-size.html [ Failure ]

third_party/blink/renderer/core/layout/layout_block_flow.cc

@@ -2514,6 +2514,10 @@ scoped_refptr<NGLayoutResult> LayoutBlockFlow::CachedLayoutResult(
   return nullptr;
 }
 
+const NGConstraintSpace* LayoutBlockFlow::CachedConstraintSpace() const {
+  return nullptr;
+}
+
 scoped_refptr<NGLayoutResult> LayoutBlockFlow::CachedLayoutResultForTesting() {
   return nullptr;
 }

third_party/blink/renderer/core/layout/layout_block_flow.h

@@ -458,6 +458,7 @@ class CORE_EXPORT LayoutBlockFlow : public LayoutBlock {
   virtual scoped_refptr<NGLayoutResult> CachedLayoutResult(
       const NGConstraintSpace&,
       NGBreakToken*) const;
+  virtual const NGConstraintSpace* CachedConstraintSpace() const;
   virtual scoped_refptr<NGLayoutResult> CachedLayoutResultForTesting();
   virtual void SetCachedLayoutResult(const NGConstraintSpace&,
                                      NGBreakToken*,

third_party/blink/renderer/core/layout/layout_flexible_box.cc

@@ -36,6 +36,8 @@
 #include "third_party/blink/renderer/core/layout/layout_state.h"
 #include "third_party/blink/renderer/core/layout/layout_view.h"
 #include "third_party/blink/renderer/core/layout/min_max_size.h"
+#include "third_party/blink/renderer/core/layout/ng/layout_ng_mixin.h"
+#include "third_party/blink/renderer/core/layout/ng/ng_constraint_space.h"
 #include "third_party/blink/renderer/core/layout/text_autosizer.h"
 #include "third_party/blink/renderer/core/paint/block_painter.h"
 #include "third_party/blink/renderer/core/paint/paint_layer.h"
@@ -825,6 +827,30 @@ void LayoutFlexibleBox::ClearCachedMainSizeForChild(const LayoutBox& child) {
   intrinsic_size_along_main_axis_.erase(&child);
 }
 
+bool LayoutFlexibleBox::ShouldForceLayoutForNGChild(
+    const LayoutBlockFlow& child) const {
+  // If the last layout was done with a different override size,
+  // or different definite-ness, we need to force-relayout so
+  // that percentage sizes are resolved correctly.
+  const NGConstraintSpace* old_space = child.CachedConstraintSpace();
+  if (!old_space)
+    return true;
+  if (old_space->IsFixedSizeInline() != child.HasOverrideLogicalWidth())
+    return true;
+  if (old_space->IsFixedSizeBlock() != child.HasOverrideLogicalHeight())
+    return true;
+  if (old_space->FixedSizeBlockIsDefinite() !=
+      UseOverrideLogicalHeightForPerentageResolution(child))
+    return true;
+  if (child.HasOverrideLogicalWidth() &&
+      old_space->AvailableSize().inline_size != child.OverrideLogicalWidth())
+    return true;
+  if (child.HasOverrideLogicalHeight() &&
+      old_space->AvailableSize().block_size != child.OverrideLogicalHeight())
+    return true;
+  return false;
+}
+
 DISABLE_CFI_PERF
 LayoutUnit LayoutFlexibleBox::ComputeInnerFlexBaseSizeForChild(
     LayoutBox& child,
@@ -1464,12 +1490,10 @@ void LayoutFlexibleBox::LayoutLineItems(FlexLine* current_line,
     }
     // We may have already forced relayout for orthogonal flowing children in
     // computeInnerFlexBaseSizeForChild.
-    // TODO(crbug.com/839661): LayoutNG does not correctly set
-    // HasPercentHeightDescendants(), so we need to bypass this optimization
-    // for now.
     bool force_child_relayout =
         relayout_children && !relaid_out_children_.Contains(child);
-    if (RuntimeEnabledFeatures::LayoutNGEnabled() ||
+    if ((child->IsLayoutNGMixin() &&
+         ShouldForceLayoutForNGChild(ToLayoutBlockFlow(*child))) ||
         (child->IsLayoutBlock() &&
          ToLayoutBlock(*child).HasPercentHeightDescendants())) {
       // Have to force another relayout even though the child is sized

third_party/blink/renderer/core/layout/layout_flexible_box.h

@@ -158,6 +158,7 @@ class CORE_EXPORT LayoutFlexibleBox : public LayoutBlock {
   EOverflow MainAxisOverflowForChild(const LayoutBox& child) const;
   EOverflow CrossAxisOverflowForChild(const LayoutBox& child) const;
   void CacheChildMainSize(const LayoutBox& child);
+  bool ShouldForceLayoutForNGChild(const LayoutBlockFlow& child) const;
 
   void LayoutFlexItems(bool relayout_children, SubtreeLayoutScope&);
   LayoutUnit AutoMarginOffsetInMainAxis(const Vector<FlexItem>&,

third_party/blink/renderer/core/layout/ng/layout_ng_mixin.cc

@@ -167,6 +167,11 @@ scoped_refptr<NGLayoutResult> LayoutNGMixin<Base>::CachedLayoutResult(
   return cached_result_->CloneWithoutOffset();
 }
 
+template <typename Base>
+const NGConstraintSpace* LayoutNGMixin<Base>::CachedConstraintSpace() const {
+  return cached_constraint_space_.get();
+}
+
 template <typename Base>
 void LayoutNGMixin<Base>::SetCachedLayoutResult(
     const NGConstraintSpace& constraint_space,

third_party/blink/renderer/core/layout/ng/layout_ng_mixin.h

@@ -58,6 +58,7 @@ class CORE_TEMPLATE_CLASS_EXPORT LayoutNGMixin : public Base {
   scoped_refptr<NGLayoutResult> CachedLayoutResult(
       const NGConstraintSpace&,
       NGBreakToken*) const override;
+  const NGConstraintSpace* CachedConstraintSpace() const override;
 
   void SetCachedLayoutResult(const NGConstraintSpace&,
                              NGBreakToken*,