[omnibox] Break out SetCaretPos() method and enhance browser test

ios/chrome/browser/ui/omnibox/omnibox_view_ios.h

 // Copyright (c) 2012 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 IOS_CHROME_BROWSER_UI_OMNIBOX_OMNIBOX_VIEW_IOS_H_
 #define IOS_CHROME_BROWSER_UI_OMNIBOX_OMNIBOX_VIEW_IOS_H_
 
 #import <UIKit/UIKit.h>
 
 #include <memory>
@@ skipping 38 matching lines @@
   void OpenMatch(const AutocompleteMatch& match,
                  WindowOpenDisposition disposition,
                  const GURL& alternate_nav_url,
                  const base::string16& pasted_text,
                  size_t selected_line) override;
   base::string16 GetText() const override;
   void SetWindowTextAndCaretPos(const base::string16& text,
                                 size_t caret_pos,
                                 bool update_popup,
                                 bool notify_text_changed) override;
+  void SetCaretPos(size_t caret_pos) override;
   void RevertAll() override;
   void UpdatePopup() override;
   void OnTemporaryTextMaybeChanged(const base::string16& display_text,
                                    bool save_original_selection,
                                    bool notify_text_changed) override;
   bool OnInlineAutocompleteTextMaybeChanged(const base::string16& display_text,
                                             size_t user_text_length) override;
   void OnBeforePossibleChange() override;
   bool OnAfterPossibleChange(bool allow_keyword_ui_change) override;
   bool IsImeComposing() const override;
@@ skipping 112 matching lines @@
 
   // Bridges delegate method calls from |field_| to C++ land.
   base::scoped_nsobject<AutocompleteTextFieldDelegate> field_delegate_;
 
   // Temporary pointer to the attributed display string, stored as color and
   // other emphasis attributes are applied by the superclass.
   NSMutableAttributedString* attributing_display_string_;  // weak
 };
 
 #endif  // IOS_CHROME_BROWSER_UI_OMNIBOX_OMNIBOX_VIEW_IOS_H_