[Idle time spell checker] Correct position passed from undo stack

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

Index: third_party/WebKit/Source/core/editing/spellcheck/IdleSpellCheckCallback.cpp
diff --git a/third_party/WebKit/Source/core/editing/spellcheck/IdleSpellCheckCallback.cpp b/third_party/WebKit/Source/core/editing/spellcheck/IdleSpellCheckCallback.cpp
index 41211b259bc2165bbe308c0610578816aa8d4a08..18cc6797d2b34ce1290e6fa417a29fee0804ee52 100644
--- a/third_party/WebKit/Source/core/editing/spellcheck/IdleSpellCheckCallback.cpp
+++ b/third_party/WebKit/Source/core/editing/spellcheck/IdleSpellCheckCallback.cpp
@@ -34,6 +34,13 @@ const int kInvalidHandle = -1;
 const int kDummyHandleForForcedInvocation = -2;
 const double kForcedInvocationDeadlineSeconds = 10;
 
+Position CorrectedReferencePosition(const Position& position,
+                                    const Document& document) {
+  if (!position.IsConnected() || position.GetDocument() != document)
+    return Position();
+  return CreateVisiblePosition(position).DeepEquivalent();
+}
+
 }  // namespace
 
 IdleSpellCheckCallback::~IdleSpellCheckCallback() {}
@@ -155,7 +162,13 @@ void IdleSpellCheckCallback::HotModeInvocation(IdleDeadline* deadline) {
         std::max(step->SequenceNumber(), last_processed_undo_step_sequence_);
     if (deadline->timeRemaining() == 0)
       break;
-    requester.CheckSpellingAt(step->EndingSelection().Extent());
+    // The reference position stored in undo stack can be invalid, disconnected
+    // or have been moved to another document, in which case it should be
+    // corrected.
+    const Position& stored_position = step->EndingSelection().Extent();
+    const Position& corrected_position =
+        CorrectedReferencePosition(stored_position, *GetFrame().GetDocument());
+    requester.CheckSpellingAt(corrected_position);
   }
 }