Reland "[LayoutNG] Turn AssertLaidOut into a CHECK for LayoutNG"

This reverts commit ec11fe81.

Reason for revert: Try to catch more crashes in the wild after
a fix (crrev.com/c/1546713) has been landed.

Original change's description:
> Revert "[LayoutNG] Turn AssertLaidOut into a CHECK for LayoutNG"
> 
> This reverts commit bade42c5.
> 
> Reason for revert: New crashes already caught. Reverting CHECKs
> back into DCHECKs to reduce noises.
> 
> Original change's description:
> > [LayoutNG] Turn AssertLaidOut into a CHECK for LayoutNG
> > 
> > Bug: 946004
> > Change-Id: I9e2aa69a32f7a0373196d57e629256dbc7d78d2a
> > Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1540305
> > Reviewed-by: Koji Ishii <kojii@chromium.org>
> > Reviewed-by: Emil A Eklund <eae@chromium.org>
> > Commit-Queue: Xiaocheng Hu <xiaochengh@chromium.org>
> > Cr-Commit-Position: refs/heads/master@{#644907}
> 
> TBR=eae@chromium.org,kojii@chromium.org,xiaochengh@chromium.org
> 
> Change-Id: I15fb43370f58757e09e7b7abc7c40d4af4a6101a
> No-Presubmit: true
> No-Tree-Checks: true
> No-Try: true
> Bug: 946004
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1544156
> Reviewed-by: Xiaocheng Hu <xiaochengh@chromium.org>
> Commit-Queue: Xiaocheng Hu <xiaochengh@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#645407}

TBR=eae@chromium.org,kojii@chromium.org,xiaochengh@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 946004
Change-Id: Iccb8c2b998d28f659381c3f89a1686614600860c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1548248Reviewed-by: Xiaocheng Hu <xiaochengh@chromium.org>
Commit-Queue: Xiaocheng Hu <xiaochengh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#646516}

third_party/blink/renderer/core/frame/local_frame_view.cc

@@ -961,11 +961,11 @@ void LocalFrameView::UpdateLayout() {
   if (nested_layout_count_)
     return;
 
-#if DCHECK_IS_ON()
+  // TODO(crbug.com/946004): Move the following line into a DCHECK_IS_ON() block
+  // when we no longer see missing layout reports in LayoutNG.
   // Post-layout assert that nobody was re-marked as needing layout during
   // layout.
   GetLayoutView()->AssertSubtreeIsLaidOut();
-#endif
 
   if (frame_->IsMainFrame()) {
     // Scrollbars changing state can cause a visual viewport size change.
@@ -2884,9 +2884,9 @@ void LocalFrameView::UpdateStyleAndLayoutIfNeededRecursive() {
   // These asserts ensure that parent frames are clean, when child frames
   // finished updating layout and style.
   CheckDoesNotNeedLayout();
-#if DCHECK_IS_ON()
+  // TODO(crbug.com/946004): Move the following line into a DCHECK_IS_ON() block
+  // when we no longer see missing layout reports in LayoutNG.
   frame_->GetDocument()->GetLayoutView()->AssertLaidOut();
-#endif
 
   UpdateGeometriesIfNeeded();
 

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

@@ -392,6 +392,11 @@ class CORE_EXPORT LayoutObject : public ImageResourceObserver,
     LayoutObject& layout_object_;
     bool preexisting_forbidden_;
   };
+#endif  // DCHECK_IS_ON()
+
+  // TODO(crbug.com/946004): When we no longer see missing layouts in LayoutNG,
+  // move the following two functions back to the DCHECK_IS_ON() block and
+  // remove relevant branches and CHECK.
 
   void AssertLaidOut() const {
 #ifndef NDEBUG
@@ -399,9 +404,16 @@ class CORE_EXPORT LayoutObject : public ImageResourceObserver,
       ShowLayoutTreeForThis();
 #endif
     SECURITY_DCHECK(!NeedsLayout() || LayoutBlockedByDisplayLock());
+    if (!RuntimeEnabledFeatures::LayoutNGEnabled())
+      return;
+    CHECK(!NeedsLayout() || LayoutBlockedByDisplayLock()) << this;
   }
 
   void AssertSubtreeIsLaidOut() const {
+#if !DCHECK_IS_ON()
+    if (!RuntimeEnabledFeatures::LayoutNGEnabled())
+      return;
+#endif
     for (const LayoutObject* layout_object = this; layout_object;
          layout_object = layout_object->LayoutBlockedByDisplayLock()
                              ? layout_object->NextInPreOrderAfterChildren()
@@ -410,6 +422,7 @@ class CORE_EXPORT LayoutObject : public ImageResourceObserver,
     }
   }
 
+#if DCHECK_IS_ON()
   void AssertClearedPaintInvalidationFlags() const {
 #ifndef NDEBUG
     if (PaintInvalidationStateIsDirty() && !PrePaintBlockedByDisplayLock()) {
@@ -428,7 +441,7 @@ class CORE_EXPORT LayoutObject : public ImageResourceObserver,
     }
   }
 
-#endif
+#endif  // DCHECK_IS_ON()
 
   // LayoutObject tree manipulation
   //////////////////////////////////////////