Expand TextCheckingParagraph::OffsetTo() into SelectionController::MarkAndReplaceFor()

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

Index: third_party/WebKit/Source/core/editing/spellcheck/SpellChecker.cpp
diff --git a/third_party/WebKit/Source/core/editing/spellcheck/SpellChecker.cpp b/third_party/WebKit/Source/core/editing/spellcheck/SpellChecker.cpp
index 9ebfbdeacce016b2e65697de247f07545357f17c..c8432e8782a2568a4c5e24d5aa1bc3708f2b3e91 100644
--- a/third_party/WebKit/Source/core/editing/spellcheck/SpellChecker.cpp
+++ b/third_party/WebKit/Source/core/editing/spellcheck/SpellChecker.cpp
@@ -604,7 +604,6 @@ void SpellChecker::MarkAndReplaceFor(
   // and should be rewritten.
   // Expand the range to encompass entire paragraphs, since text checking needs
   // that much context.
-  int selection_offset = 0;
   int ambiguous_boundary_offset = -1;
 
   if (GetFrame().Selection().ComputeVisibleSelectionInDOMTree().IsCaret()) {
@@ -613,7 +612,11 @@ void SpellChecker::MarkAndReplaceFor(
     // Attempt to save the caret position so we can restore it later if needed
     const Position& caret_position =
         GetFrame().Selection().ComputeVisibleSelectionInDOMTree().end();
-    selection_offset = paragraph.OffsetTo(caret_position);
+    const Position& paragraph_start = checking_range.StartPosition();
+    const int selection_offset =
+        paragraph_start < caret_position
+            ? TextIterator::RangeLength(paragraph_start, caret_position)
+            : 0;
     if (selection_offset > 0 &&
         static_cast<unsigned>(selection_offset) <=
             paragraph.GetText().length() &&