Remove false assertion in ApplyBlockElementCommand::formatSelection()

Source/core/editing/ApplyBlockElementCommand.cpp

 /*
  * Copyright (C) 2006, 2008 Apple Inc. All rights reserved.
  * Copyright (C) 2010 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 128 matching lines @@
         // the next paragraph is in the same cell.
         if (enclosingCell && enclosingCell != enclosingNodeOfType(endOfNextParagraph.deepEquivalent(), &isTableCell))
             blockquoteForNextIndent = 0;
 
         // indentIntoBlockquote could move more than one paragraph if the paragraph
         // is in a list item or a table. As a result, endAfterSelection could refer to a position
         // no longer in the document.
         if (endAfterSelection.isNotNull() && !endAfterSelection.deepEquivalent().inDocument())
             break;
         // Sanity check: Make sure our moveParagraph calls didn't remove endOfNextParagraph.deepEquivalent().deprecatedNode()
-        // If somehow we did, return to prevent crashes.
-        if (endOfNextParagraph.isNotNull() && !endOfNextParagraph.deepEquivalent().inDocument()) {
-            ASSERT_NOT_REACHED();
+        // If somehow, e.g. mutation event handler, we did, return to prevent crashes.
+        if (endOfNextParagraph.isNotNull() && !endOfNextParagraph.deepEquivalent().inDocument())
             return;
-        }
         endOfCurrentParagraph = endOfNextParagraph;
     }
 }
 
 static bool isNewLineAtPosition(const Position& position)
 {
     Node* textNode = position.containerNode();
     int offset = position.offsetInContainerNode();
     if (!textNode || !textNode->isTextNode() || offset < 0 || offset >= textNode->maxCharacterOffset())
         return false;
@@ skipping 116 matching lines @@
 
 PassRefPtr<Element> ApplyBlockElementCommand::createBlockElement() const
 {
     RefPtr<Element> element = createHTMLElement(document(), m_tagName);
     if (m_inlineStyle.length())
         element->setAttribute(styleAttr, m_inlineStyle);
     return element.release();
 }
 
 }