Ensure valid VisiblePosition input for inSameBlock

third_party/WebKit/Source/core/editing/VisibleUnits.cpp

 /*
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009 Apple 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
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 1905 matching lines @@
 VisiblePosition endOfBlock(const VisiblePosition& visiblePosition, EditingBoundaryCrossingRule rule)
 {
     DCHECK(visiblePosition.isValid()) << visiblePosition;
     Position position = visiblePosition.deepEquivalent();
     Element* endBlock = position.computeContainerNode() ? enclosingBlock(position.computeContainerNode(), rule) : 0;
     return endBlock ? VisiblePosition::lastPositionInNode(endBlock) : VisiblePosition();
 }
 
 bool inSameBlock(const VisiblePosition& a, const VisiblePosition& b)
 {
-    // TODO(xiaochengh): Ensure that this function is called with valid |a| and
-    // |b|, and add |DCHECK(a.isValid())| and |DCHECK(b.isValid())|
+    DCHECK(a.isValid()) << a;
+    DCHECK(b.isValid()) << b;
     return !a.isNull() && enclosingBlock(a.deepEquivalent().computeContainerNode()) == enclosingBlock(b.deepEquivalent().computeContainerNode());
 }
 
 bool isStartOfBlock(const VisiblePosition& pos)
 {
     DCHECK(pos.isValid()) << pos;
     return pos.isNotNull() && pos.deepEquivalent() == startOfBlock(pos, CanCrossEditingBoundary).deepEquivalent();
 }
 
 bool isEndOfBlock(const VisiblePosition& pos)
@@ skipping 1542 matching lines @@
 {
     return previousPositionOfAlgorithm<EditingStrategy>(visiblePosition, rule);
 }
 
 VisiblePositionInFlatTree previousPositionOf(const VisiblePositionInFlatTree& visiblePosition, EditingBoundaryCrossingRule rule)
 {
     return previousPositionOfAlgorithm<EditingInFlatTreeStrategy>(visiblePosition, rule);
 }
 
 } // namespace blink