Prevent copyTextTo() from Breaking Code Points

third_party/WebKit/Source/core/editing/iterators/SimplifiedBackwardsTextIterator.cpp

Index: third_party/WebKit/Source/core/editing/iterators/SimplifiedBackwardsTextIterator.cpp
diff --git a/third_party/WebKit/Source/core/editing/iterators/SimplifiedBackwardsTextIterator.cpp b/third_party/WebKit/Source/core/editing/iterators/SimplifiedBackwardsTextIterator.cpp
index 32f93982f086aafa14c9e041420ac751e502d65d..3d8aeab7673cc8d8e41059adffc7ebadd6fadcd2 100644
--- a/third_party/WebKit/Source/core/editing/iterators/SimplifiedBackwardsTextIterator.cpp
+++ b/third_party/WebKit/Source/core/editing/iterators/SimplifiedBackwardsTextIterator.cpp
@@ -403,6 +403,13 @@ UChar SimplifiedBackwardsTextIteratorAlgorithm<Strategy>::characterAt(unsigned i
     return m_textContainer[m_textOffset + m_textLength - 1 - index];
 }
 
+template <typename Strategy>
+bool SimplifiedBackwardsTextIteratorAlgorithm<Strategy>::isBetweenSurrogatePair(int position) const
+{
+    ASSERT(position >= 0);
+    return position > 0 && position < length() && U16_IS_TRAIL(characterAt(position - 1)) && U16_IS_LEAD(characterAt(position));
+}
+
 template class CORE_TEMPLATE_EXPORT SimplifiedBackwardsTextIteratorAlgorithm<EditingStrategy>;
 template class CORE_TEMPLATE_EXPORT SimplifiedBackwardsTextIteratorAlgorithm<EditingInComposedTreeStrategy>;