Introduce CompositeEditCommand::RemoveAllChildrenIfPossible()

This patch Introduces |CompositeEditCommand::RemoveAllChildrenIfPossible()|
to avoid infinite root in |TypingCommand| and |DeleteSelectionCommand|.

This patch is a continuation of the CL[1].

Note: no regression test as there's no minimized test case in the original
report, and it's not worth the minimization because the bug is a rather
edge case that requires an editable <style> element that specifies editable
style on its parent using deprecated '-webkit-user-modify'.

[1] http://crrev.com/c/1567098 [Editing] Abort TypingCommand when RemoveNode()
fails to remove a node

Bug: 949501
Change-Id: I9bd19da22f54cd7cbda735103c599a5082f8d94f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1573434
Auto-Submit: Yoshifumi Inoue <yosin@chromium.org>
Reviewed-by: Xiaocheng Hu <xiaochengh@chromium.org>
Commit-Queue: Yoshifumi Inoue <yosin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#652465}

third_party/blink/renderer/core/editing/commands/composite_edit_command.cc

@@ -373,6 +373,25 @@ void CompositeEditCommand::AppendNode(Node* node,
                           editing_state);
 }
 
+void CompositeEditCommand::RemoveAllChildrenIfPossible(
+    ContainerNode* container,
+    EditingState* editing_state,
+    ShouldAssumeContentIsAlwaysEditable
+        should_assume_content_is_always_editable) {
+  Node* child = container->firstChild();
+  while (child) {
+    Node* const next = child->nextSibling();
+    RemoveNode(child, editing_state, should_assume_content_is_always_editable);
+    if (editing_state->IsAborted())
+      return;
+    if (next && next->parentNode() != container) {
+      // |RemoveNode()| moves |next| outside |node|.
+      return;
+    }
+    child = next;
+  }
+}
+
 void CompositeEditCommand::RemoveChildrenInRange(Node* node,
                                                  unsigned from,
                                                  unsigned to,

third_party/blink/renderer/core/editing/commands/composite_edit_command.h

@@ -130,6 +130,11 @@ class CORE_EXPORT CompositeEditCommand : public EditCommand {
   bool CanRebalance(const Position&) const;
   void RemoveCSSProperty(Element*, CSSPropertyID);
   void RemoveElementAttribute(Element*, const QualifiedName& attribute);
+  // Remove all children if possible
+  void RemoveAllChildrenIfPossible(ContainerNode*,
+                                   EditingState*,
+                                   ShouldAssumeContentIsAlwaysEditable =
+                                       kDoNotAssumeContentIsAlwaysEditable);
   void RemoveChildrenInRange(Node*, unsigned from, unsigned to, EditingState*);
   virtual void RemoveNode(Node*,
                           EditingState*,

third_party/blink/renderer/core/editing/commands/delete_selection_command.cc

@@ -479,21 +479,10 @@ void DeleteSelectionCommand::RemoveNode(
       if (!node->hasChildren())
         return;
       // Search this non-editable region for editable regions to empty.
-      Node* child = node->firstChild();
-      while (child) {
-        Node* next_child = child->nextSibling();
-        RemoveNode(child, editing_state,
-                   should_assume_content_is_always_editable);
-        if (editing_state->IsAborted())
-          return;
-        // Bail if nextChild is no longer node's child.
-        if (next_child && next_child->parentNode() != node)
-          return;
-        child = next_child;
-      }
-
       // Don't remove editable regions that are inside non-editable ones, just
       // clear them.
+      RemoveAllChildrenIfPossible(ToContainerNode(node), editing_state,
+                                  should_assume_content_is_always_editable);
       return;
     }
   }
@@ -501,15 +490,10 @@ void DeleteSelectionCommand::RemoveNode(
   if (IsTableStructureNode(node) || IsRootEditableElement(*node)) {
     // Do not remove an element of table structure; remove its contents.
     // Likewise for the root editable element.
-    Node* child = node->firstChild();
-    while (child) {
-      Node* remove = child;
-      child = child->nextSibling();
-      RemoveNode(remove, editing_state,
-                 should_assume_content_is_always_editable);
-      if (editing_state->IsAborted())
-        return;
-    }
+    RemoveAllChildrenIfPossible(ToContainerNode(node), editing_state,
+                                should_assume_content_is_always_editable);
+    if (editing_state->IsAborted())
+      return;
 
     // Make sure empty cell has some height, if a placeholder can be inserted.
     GetDocument().UpdateStyleAndLayout();

third_party/blink/renderer/core/editing/commands/typing_command.cc

@@ -737,11 +737,9 @@ bool TypingCommand::MakeEditableRootEmpty(EditingState* editing_state) {
     }
   }
 
-  while (Node* child = root->firstChild()) {
-    RemoveNode(child, editing_state);
-    if (editing_state->IsAborted())
-      return false;
-  }
+  RemoveAllChildrenIfPossible(root, editing_state);
+  if (editing_state->IsAborted() || root->firstChild())
+    return false;
 
   AddBlockPlaceholderIfNeeded(root, editing_state);
   if (editing_state->IsAborted())