Add functions searching a word boundary without VisualPosition to HTMLTextFormControlElement.

Source/core/html/HTMLTextFormControlElement.h

Index: Source/core/html/HTMLTextFormControlElement.h
diff --git a/Source/core/html/HTMLTextFormControlElement.h b/Source/core/html/HTMLTextFormControlElement.h
index 6d1c5921f2faf1f00991e1d57d71b22755c95255..403de83eea28b98e7b560dd8a8ed0336f897da55 100644
--- a/Source/core/html/HTMLTextFormControlElement.h
+++ b/Source/core/html/HTMLTextFormControlElement.h
@@ -87,6 +87,14 @@ public:
 
     void setTextAsOfLastFormControlChangeEvent(const String& text) { m_textAsOfLastFormControlChangeEvent = text; }
 
+    // These functions don't cause synchronous layout and SpellChecker uses
+    // them to improve performance.
+    // Passed |Position| must point inside of a text form control.
+    static Position startOfWord(const Position&);
+    static Position endOfWord(const Position&);
+    static Position startOfSentence(const Position&);
+    static Position endOfSentence(const Position&);
+
 protected:
     HTMLTextFormControlElement(const QualifiedName&, Document&, HTMLFormElement*);
     bool isPlaceholderEmpty() const;