Implement double/triple click functionality 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 176bc6e6a5b427af2d113a52b77e3dbef5ae9f18..00d27e5519717cd057d374f69ec700cde7331c7a 100644
--- a/views/controls/textfield/textfield_views_model.h
+++ b/views/controls/textfield/textfield_views_model.h
@@ -117,6 +117,9 @@ class TextfieldViewsModel {
   // Selects all text.
   void SelectAll();
 
+  // Selects the word at which the cursor is currently positioned.
+  void SelectWord();
+
   // Clears selection.
   void ClearSelection();
 
@@ -149,6 +152,9 @@ class TextfieldViewsModel {
   // Returns the visible text given |start| and |end|.
   string16 GetVisibleText(size_t start, size_t end) const;
 
+  // Utility for SelectWord(). Checks whether position pos is at word boundary.
+  bool IsPositionAtWordSelectionBoundary(size_t pos);
+
   // The text in utf16 format.
   string16 text_;