Make InsertIncrementalTextCommand to handle surrogate pair

third_party/WebKit/Source/core/editing/commands/InsertIncrementalTextCommand.h

 // Copyright (c) 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef InsertIncrementalTextCommand_h
 #define InsertIncrementalTextCommand_h
 
 #include "core/editing/commands/InsertTextCommand.h"
 
 namespace blink {
 
-class InsertIncrementalTextCommand final : public InsertTextCommand {
+class CORE_EXPORT InsertIncrementalTextCommand final
+    : public InsertTextCommand {
  public:
   static InsertIncrementalTextCommand* create(
       Document&,
       const String&,
       bool selectInsertedText = false,
       RebalanceType = RebalanceLeadingAndTrailingWhitespaces);
 
  private:
   InsertIncrementalTextCommand(Document&,
                                const String& text,
                                bool selectInsertedText,
                                RebalanceType);
   void doApply(EditingState*) override;
 };
 
 }  // namespace blink
 
 #endif  // InsertIncrementalTextCommand_h