InstantExtended: add a finch flag to disable Instant Extended on SRP.

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 119 matching lines @@
 // Exposed for testing.
 bool ShouldUseCacheableNTP();
 
 // Returns true if the Instant NTP should be shown and false if not.
 bool ShouldShowInstantNTP();
 
 // Returns true if the recent tabs link should be shown on the local NTP in
 // field trials.
 bool ShouldShowRecentTabsOnNTP();
 
+// Returns true if Instant Extended should be disabled on the search results
+// page.
+bool ShouldSuppressInstantExtendedOnSRP();
+
 // Returns true if |my_url| matches |other_url|.
 bool MatchesOriginAndPath(const GURL& my_url, const GURL& other_url);
 
 // Transforms the input |url| into its "effective URL". The returned URL
 // facilitates grouping process-per-site. The |url| is transformed, for
 // example, from
 //
 //   https://www.google.com/search?espv=1&q=tractors
 //
 // to the privileged URL
@@ skipping 84 matching lines @@
                                     bool default_value,
                                     const FieldTrialFlags& flags);
 
 // Let tests reset the gate that prevents metrics from being sent more than
 // once.
 void ResetInstantExtendedOptInStateGateForTest();
 
 }  // namespace chrome
 
 #endif  // CHROME_BROWSER_SEARCH_SEARCH_H_