Don't merge replace edit if previous edit is delete edit.

ui/views/controls/textfield/textfield_views_model.cc

 // Copyright (c) 2011 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 "ui/views/controls/textfield/textfield_views_model.h"
 
 #include <algorithm>
 
 #include "base/i18n/break_iterator.h"
 #include "base/logging.h"
@@ skipping 40 matching lines @@
   void Redo(TextfieldViewsModel* model) {
     model->ModifyText(old_text_start_, old_text_end(),
                       new_text_, new_text_start_,
                       new_cursor_pos_);
   }
 
   // Try to merge the |edit| into this edit. Returns true if merge was
   // successful, or false otherwise. Merged edit will be deleted after
   // redo and should not be reused.
   bool Merge(const Edit* edit) {
-    if (edit->merge_with_previous()) {
-      MergeSet(edit);
+    // Don't merge if previous edit is DELETE. This happens when a
+    // user deletes characters then hits return. In this case, the
+    // delete should be treated as separate edit that can be undone
+    // and should not be merged with the replace edit.
+    if (type_ != DELETE_EDIT && edit->merge_with_previous()) {
+      MergeReplace(edit);
       return true;
     }
     return mergeable() && edit->mergeable() && DoMerge(edit);
   }
 
   // Commits the edit and marks as un-mergeable.
   void Commit() { merge_type_ = DO_NOT_MERGE; }
 
  private:
   friend class InsertEdit;
@@ skipping 33 matching lines @@
   bool merge_with_previous() const {
     return merge_type_ == MERGE_WITH_PREVIOUS;
   }
 
   // Returns the end index of the |old_text_|.
   size_t old_text_end() const { return old_text_start_ + old_text_.length(); }
 
   // Returns the end index of the |new_text_|.
   size_t new_text_end() const { return new_text_start_ + new_text_.length(); }
 
-  // Merge the Set edit into the current edit. This is a special case to
+  // Merge the replace edit into the current edit. This is a special case to
   // handle an omnibox setting autocomplete string after new character is
   // typed in.
-  void MergeSet(const Edit* edit) {
+  void MergeReplace(const Edit* edit) {
     CHECK_EQ(REPLACE_EDIT, edit->type_);
     CHECK_EQ(0U, edit->old_text_start_);
     CHECK_EQ(0U, edit->new_text_start_);
     string16 old_text = edit->old_text_;
     old_text.erase(new_text_start_, new_text_.length());
     old_text.insert(old_text_start_, old_text_);
     // SetText() replaces entire text. Set |old_text_| to the entire
     // replaced text with |this| edit undone.
     old_text_ = old_text;
     old_text_start_ = edit->old_text_start_;
@@ skipping 656 matching lines @@
   if (delete_from != delete_to)
     render_text_->SetText(text.erase(delete_from, delete_to - delete_from));
   if (!new_text.empty())
     render_text_->SetText(text.insert(new_text_insert_at, new_text));
   render_text_->SetCursorPosition(new_cursor_pos);
   // TODO(oshima): mac selects the text that is just undone (but gtk doesn't).
   // This looks fine feature and we may want to do the same.
 }
 
 }  // namespace views