Introduce DCHECK() in expandToParagraphBoundary()

third_party/WebKit/Source/core/editing/spellcheck/TextCheckingHelper.cpp

 /*
  * Copyright (C) 2006, 2007 Apple Inc. All rights reserved.
  * Copyright (C) 2008 Nokia Corporation and/or its subsidiary(-ies)
  *
  * 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 79 matching lines @@
             misspelling.length = misspellingLength;
             results.append(misspelling);
         }
 
         wordStart = wordEnd;
     }
 }
 
 static EphemeralRange expandToParagraphBoundary(const EphemeralRange& range)
 {
-    return EphemeralRange(startOfParagraph(createVisiblePosition(range.startPosition())).deepEquivalent(), endOfParagraph(createVisiblePosition(range.endPosition())).deepEquivalent());
+    const VisiblePosition& start = createVisiblePosition(range.startPosition());
+    DCHECK(start.isNotNull()) << range.startPosition();
+    const VisiblePosition& paragraphStart = startOfParagraph(start);
+    DCHECK(paragraphStart.isNotNull()) << range.startPosition();
+
+    const VisiblePosition& end = createVisiblePosition(range.endPosition());
+    DCHECK(end.isNotNull()) << range.endPosition();
+    const VisiblePosition& paragraphEnd = endOfParagraph(end);
+    DCHECK(paragraphEnd.isNotNull()) << range.endPosition();
+
+    return EphemeralRange(paragraphStart.deepEquivalent(), paragraphEnd.deepEquivalent());
 }
 
 TextCheckingParagraph::TextCheckingParagraph(const EphemeralRange& checkingRange)
     : m_checkingRange(checkingRange)
     , m_checkingStart(-1)
     , m_checkingEnd(-1)
     , m_checkingLength(-1)
 {
 }
 
@@ skipping 453 matching lines @@
         return false;
 
     const Settings* settings = frame->settings();
     if (!settings)
         return false;
 
     return settings->unifiedTextCheckerEnabled();
 }
 
 } // namespace blink