Implement clipboard features in views textfield.

views/controls/textfield/textfield_views_model.h

Index: views/controls/textfield/textfield_views_model.h
diff --git a/views/controls/textfield/textfield_views_model.h b/views/controls/textfield/textfield_views_model.h
index 219a8c721617014cf9360b03163f873e11c9377f..6bc0464abad0b5fb3c1e1140f930b4c0e73dbf74 100644
--- a/views/controls/textfield/textfield_views_model.h
+++ b/views/controls/textfield/textfield_views_model.h
@@ -8,6 +8,7 @@
 
 #include <vector>
 
+#include "app/keyboard_codes.h"
 #include "base/string16.h"
 #include "gfx/rect.h"
 #include "third_party/skia/include/core/SkColor.h"
@@ -126,6 +127,10 @@ class TextfieldViewsModel {
     return GetVisibleText(0U, text_.length());
   }
 
+  // Handles key event for Cut/Copy/Paste key presses. Returns true if text
+  // has changed after handling the event (in case of cut and paste events).
+  bool HandleClipboardEvents(app::KeyboardCode key_code);
+
  private:
   friend class NativeTextfieldViews;