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

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

 // 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.
 
 #include "ios/chrome/browser/ui/omnibox/omnibox_view_ios.h"
 
 #import <CoreText/CoreText.h>
 #import <MobileCoreServices/MobileCoreServices.h>
 
 #include "base/auto_reset.h"
@@ skipping 224 matching lines @@
   NSAttributedString* as = ApplyTextAttributes(text);
   [field_ setText:as userTextLength:[as length]];
 
   if (update_popup)
     UpdatePopup();
 
   if (notify_text_changed)
     model()->OnChanged();
 }
 
+// TODO(crbug.com/726702): Implement this and have |SetWindowTextAndCaretPos()|
+// call it.
+void OmniboxViewIOS::SetCaretPos(size_t caret_pos) {}
+
 void OmniboxViewIOS::RevertAll() {
   ignore_popup_updates_ = true;
   OmniboxView::RevertAll();
   ignore_popup_updates_ = false;
 }
 
 void OmniboxViewIOS::UpdatePopup() {
   model()->SetInputInProgress(true);
 
   if (!model()->has_focus())
@@ skipping 630 matching lines @@
 // is being left out for now because it was not present before the OmniboxView
 // rewrite.
 #if 0
   // When editing is in progress, the url text is not colored, so there is
   // nothing to emphasize.  (Calling SetText() in that situation would also be
   // harmful, as it would reset the carat position to the end of the text.)
   if (!IsEditingOrEmpty())
     SetText(GetText());
 #endif
 }