[LayoutNG] More limited inline split fix

This testcase hit a DCHECK while rebalancing split inlines

LayoutInline::SplitInlines
  LayoutBoxModelObject::MoveChildTo

Layout tree looks like it should work. I think that our previous
fix of not splitting any anonymous inlines was incorrect.
This reverts my older fix at
https://chromium-review.googlesource.com/c/chromium/src/+/1610522/1

to a more conservative skip:

if (o->IsLayoutNGInsideListMarker())

instead of

if (o->IsAnonymous())

clusterfuzz layout tree looks like this:

    LayoutNGBlockFlow 0x71c8ea202a0  	FORM id="el0"
        LayoutNGBlockFlow (anonymous) 0x71c8ea20530
          LayoutInline (anonymous) 0x71c8ea303d0
*           LayoutInline 0x71c8ea30250 continuation=0x71c8ea203e8	Q id="el2"
              LayoutInline 0x71c8ea30310	<pseudo:before>
                LayoutQuote (anonymous) 0x71c8ea3c2f8
                  LayoutTextFragment (anonymous) 0x71c8ea40370 """
            LayoutInline 0x71c8ea30190 	Q id="el5"
              LayoutInline 0x71c8ea300d0	<pseudo:before>
                LayoutQuote (anonymous) 0x71c8ea3c108
                  LayoutTextFragment (anonymous) 0x71c8ea40130 "'"
              LayoutInline 0x71c8ea30490	<pseudo:after>
                LayoutQuote (anonymous) 0x71c8ea3c010
                  LayoutTextFragment (anonymous) 0x71c8ea4001

Bug: 962841
Change-Id: I5165089499c2ff7856f999d2926e07d4a992960d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1611866Reviewed-by: Morten Stenshorne <mstensho@chromium.org>
Reviewed-by: Emil A Eklund <eae@chromium.org>
Commit-Queue: Aleks Totic <atotic@chromium.org>
Cr-Commit-Position: refs/heads/master@{#659700}

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

@@ -612,7 +612,7 @@ void LayoutInline::SplitInlines(LayoutBlockFlow* from_block,
   Vector<LayoutInline*> inlines_to_clone;
   LayoutInline* top_most_inline = this;
   for (LayoutObject* o = this; o != from_block; o = o->Parent()) {
-    if (o->IsAnonymous())
+    if (o->IsLayoutNGInsideListMarker())
       continue;
     top_most_inline = ToLayoutInline(o);
     if (inlines_to_clone.size() < kCMaxSplitDepth)