Through code search on file CompositeEditCommand.cpp, suspected CL is
https://chromium.googlesource.com/chromium/src/+/acce62cb77947bf2f14d6c7ac74219d515a94ffb
chongz@, could you please take a look?

My bisect hints that this is a long standing issue (probably even before r200000 etc.) but I cannot locate the exact CL.

However according to the stack trace it doesn't seems to be a difficult bug, will see if I can fix it.

```
void DeleteSelectionCommand::removeRedundantBlocks(EditingState* editingState) {
  Node* node = m_endingPosition.computeContainerNode();
  LOG(ERROR) << "removeRedundantBlocks: " << node;
  Element* rootElement = rootEditableElement(*node);

  while (node && node != rootElement) {
    if (isRemovableBlock(node)) {
      if (node == m_endingPosition.anchorNode())
        updatePositionForNodeRemovalPreservingChildren(m_endingPosition, *node);

      CompositeEditCommand::removeNodePreservingChildren(node, editingState);
      if (editingState->isAborted())
        return;
      node = m_endingPosition.anchorNode();
      LOG(ERROR) << "node = m_endingPosition.anchorNode(): " << node;
    } else {
      node = node->parentNode();
      LOG(ERROR) << "node = node->parentNode(): " << node;
    }
  }
}
```

```
DeleteSelectionCommand.cpp(1022)] removeRedundantBlocks: LI (editable)
DeleteSelectionCommand.cpp(1037)] node = node->parentNode(): UL (editable)
DeleteSelectionCommand.cpp(1037)] node = node->parentNode(): DIV (editable)
DeleteSelectionCommand.cpp(1034)] node = m_endingPosition.anchorNode(): LI
DeleteSelectionCommand.cpp(1037)] node = node->parentNode(): UL
DeleteSelectionCommand.cpp(1037)] node = node->parentNode(): null
```

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/3c4ea2111cb111f66c87f8cd6bf3909eeaa15c9b

commit 3c4ea2111cb111f66c87f8cd6bf3909eeaa15c9b
Author: chongz <chongz@chromium.org>
Date: Thu Dec 22 18:54:16 2016

[Editing] Add null check in |DeleteSelectionCommand::removeRedundantBlocks()|

The root cause is we are removing & re-inserting children nodes during
|CompositeEditCommand::removeNodePreservingChildren()|, which means if the child
contains style "* {-webkit-user-modify: read-write;}" we won't be able to re-insert
it back as parent has lost editable attribute as soon as we've removed it.

BUG= 675727 

Review-Url: https://codereview.chromium.org/2595783002
Cr-Commit-Position: refs/heads/master@{#440459}

[modify] https://crrev.com/3c4ea2111cb111f66c87f8cd6bf3909eeaa15c9b/third_party/WebKit/Source/core/editing/BUILD.gn
[modify] https://crrev.com/3c4ea2111cb111f66c87f8cd6bf3909eeaa15c9b/third_party/WebKit/Source/core/editing/commands/ApplyStyleCommand.h
[add] https://crrev.com/3c4ea2111cb111f66c87f8cd6bf3909eeaa15c9b/third_party/WebKit/Source/core/editing/commands/ApplyStyleCommandTest.cpp
[modify] https://crrev.com/3c4ea2111cb111f66c87f8cd6bf3909eeaa15c9b/third_party/WebKit/Source/core/editing/commands/DeleteSelectionCommand.cpp

ClusterFuzz has detected this issue as fixed in range 440451:440487.

Detailed report: https://cluster-fuzz.appspot.com/testcase?key=4800242794102784

Fuzzer: inferno_layout_test_unmodified
Job Type: linux_debug_content_shell_drt
Platform Id: linux

Crash Type: CHECK failure
Crash Address: 
Crash State:
  node in CompositeEditCommand.cpp
  blink::CompositeEditCommand::isRemovableBlock
  blink::DeleteSelectionCommand::removeRedundantBlocks
  
Regressed: https://cluster-fuzz.appspot.com/revisions?job=linux_debug_content_shell_drt&range=388139:388165
Fixed: https://cluster-fuzz.appspot.com/revisions?job=linux_debug_content_shell_drt&range=440451:440487

Minimized Testcase (2.64 Kb): https://cluster-fuzz.appspot.com/download/AMIfv94ZvHhjFEVY0tUnt5jhZc6Vj-WRFIMwOlUl-jbFJvxsU97o-VP74cJ4NwaReSV4PBIEE8qZ1q-eGkMGeu3KXCsvHiSiyoIINmpwzPoU6PWiWgqxIY93jkdXQ60TrfwB_pT9xbMtWWmTSTtTLA1Up2mdZotImw?testcase_id=4800242794102784

See https://dev.chromium.org/Home/chromium-security/bugs/reproducing-clusterfuzz-bugs for more information.

If you suspect that the result above is incorrect, try re-doing that job on the test case report page.