Add histogram Omnibox.FocusToEditTime for time in milliseconds between a user focus and edit.

chrome/browser/ui/omnibox/omnibox_edit_model.h

 // Copyright 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 CHROME_BROWSER_UI_OMNIBOX_OMNIBOX_EDIT_MODEL_H_
 #define CHROME_BROWSER_UI_OMNIBOX_OMNIBOX_EDIT_MODEL_H_
 
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "base/memory/scoped_ptr.h"
@@ skipping 426 matching lines @@
   // not yet accepted them.  We use this to determine when we need to save
   // state (on switching tabs) and whether changes to the page URL should be
   // immediately displayed.
   // This flag will be true in a superset of the cases where the popup is open.
   bool user_input_in_progress_;
 
   // The text that the user has entered.  This does not include inline
   // autocomplete text that has not yet been accepted.
   string16 user_text_;
 
+  // We keep track of when the user last focused on the omnibox.
+  base::TimeTicks time_user_last_focused_on_omnibox_;
+
   // We keep track of when the user began modifying the omnibox text.
   // This should be valid whenever user_input_in_progress_ is true.
   base::TimeTicks time_user_first_modified_omnibox_;
 
   // When the user closes the popup, we need to remember the URL for their
   // desired choice, so that if they hit enter without reopening the popup we
   // know where to go.  We could simply rerun autocomplete in this case, but
   // we'd need to either wait for all results to come in (unacceptably slow) or
   // do the wrong thing when the user had chosen some provider whose results
   // were not returned instantaneously.
@@ skipping 104 matching lines @@
   // an exact keyword match.  If this is true then keyword mode will be
   // triggered automatically if the input is "<keyword> <search string>".  We
   // allow this when CreatedKeywordSearchByInsertingSpaceInMiddle() is true.
   // This has no effect if we're already in keyword mode.
   bool allow_exact_keyword_match_;
 
   DISALLOW_COPY_AND_ASSIGN(OmniboxEditModel);
 };
 
 #endif  // CHROME_BROWSER_UI_OMNIBOX_OMNIBOX_EDIT_MODEL_H_