Implement Composition interface for IME API

Source/core/html/ime/Composition.h

Index: Source/core/html/ime/Composition.h
diff --git a/Source/core/html/ime/Composition.h b/Source/core/html/ime/Composition.h
index a180c867ee04b86b3d343b4a05b3ef05f78ae4ab..0069969dbdb6fafef288c5a6499fa3f9613b79e4 100644
--- a/Source/core/html/ime/Composition.h
+++ b/Source/core/html/ime/Composition.h
@@ -39,29 +39,22 @@
 
 namespace WebCore {
 
+class InputMethodContext;
+
 class Composition : public RefCounted<Composition>, public ScriptWrappable {
 public:
-    static PassRefPtr<Composition> create();
+    static PassRefPtr<Composition> create(InputMethodContext*);
     ~Composition();
 
-    String text() const { return m_text; }
-    void setText(const String& text) { m_text = text; }
-
-    int selectionStart() const { return m_selectionStart; }
-    void setSelectionStart(int selectionStart) { selectionStart = m_selectionStart; }
-
-    int selectionEnd() const { return m_selectionEnd; }
-    void setSelectionEnd(int selectionEnd) { selectionEnd = m_selectionEnd; }
-
+    String text() const;
+    int selectionStart() const;
+    int selectionEnd() const;
     const Vector<unsigned>& getSegments() const;
 
 private:
-    Composition();
+    explicit Composition(InputMethodContext*);
 
-    String m_text;
-    int m_selectionStart;
-    int m_selectionEnd;
-    Vector<unsigned> m_segments;
+    InputMethodContext* m_inputMethodContext;
 };
 
 } // namespace WebCore