Set up a field trial flag to prerender Instant search base url on omnibox focus event.

chrome/browser/search/search.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_SEARCH_SEARCH_H_
 #define CHROME_BROWSER_SEARCH_SEARCH_H_
 
 #include <string>
 #include <utility>
 #include <vector>
@@ skipping 148 matching lines @@
 
 // Returns the default search engine base page URL to prefetch search results.
 // Returns an empty URL if 'prefetch_results' flag is set to false in field
 // trials.
 GURL GetSearchResultPrefetchBaseURL(Profile* profile);
 
 // Returns true if 'prefetch_results' flag is set to true in field trials to
 // prefetch high-confidence search suggestions.
 bool ShouldPrefetchSearchResults();
 
+// Returns true if 'prerender_instant_url_on_omnibox_focus' flag is enabled in
+// field trials to prerender Instant search base page when the omnibox is
+// focused.
+bool ShouldPrerenderInstantUrlOnOmniboxFocus();
+
 // Returns true if 'reuse_instant_search_base_page' flag is set to true in field
 // trials to reuse the prerendered page to commit any search query.
 bool ShouldReuseInstantSearchBasePage();
 
 // Returns the Local Instant URL of the New Tab Page.
 // TODO(kmadhusu): Remove this function and update the call sites.
 GURL GetLocalInstantURL(Profile* profile);
 
 // Returns true if 'hide_verbatim' flag is enabled in field trials
 // to hide the top match in the native suggestions dropdown if it is a verbatim
@@ skipping 96 matching lines @@
 bool GetBoolValueForFlagWithDefault(const std::string& flag,
                                     bool default_value,
                                     const FieldTrialFlags& flags);
 
 // Returns the Cacheable New Tab Page URL for the given |profile|.
 GURL GetNewTabPageURL(Profile* profile);
 
 }  // namespace chrome
 
 #endif  // CHROME_BROWSER_SEARCH_SEARCH_H_