Adds a field trial flag to control whether to use an alternate Instant search base page URL for pre…

chrome/browser/search/search.h

Index: chrome/browser/search/search.h
diff --git a/chrome/browser/search/search.h b/chrome/browser/search/search.h
index 978e394903849d5b0744778b735165d0205e8673..d0fa1ed3e6e17c4e4e474f48fb970d1d86266687 100644
--- a/chrome/browser/search/search.h
+++ b/chrome/browser/search/search.h
@@ -289,6 +289,11 @@ bool GetBoolValueForFlagWithDefault(const std::string& flag,
 // Returns the Cacheable New Tab Page URL for the given |profile|.
 GURL GetNewTabPageURL(Profile* profile);
 
+// Returns true if 'use_alternate_instant_url' flag is set to true in field
+// trials to use an alternate Instant search base page URL for prefetching
+// search results. This allows experimentation of Instant search.
+bool ShouldUseAltInstantURL();
+
 }  // namespace chrome
 
 #endif  // CHROME_BROWSER_SEARCH_SEARCH_H_