Cleanup: Remove for_search param from search::InstantExtendedEnabledParam()

components/search/search.h

Index: components/search/search.h
diff --git a/components/search/search.h b/components/search/search.h
index a8b21a472bd179a09ab053c23772a24812e6f7ba..dec3f32ef3a271ce84d56dda807d7686b1e7a900 100644
--- a/components/search/search.h
+++ b/components/search/search.h
@@ -61,11 +61,7 @@ bool GetBoolValueForFlagWithDefault(const std::string& flag,
 
 // Returns a string indicating whether InstantExtended is enabled, suitable
 // for adding as a query string param to the homepage or search requests.
-// Returns an empty string otherwise.
-//
-// |for_search| should be set to true for search requests, in which case this
-// returns a non-empty string only if query extraction is enabled.
-std::string InstantExtendedEnabledParam(bool for_search);
+std::string InstantExtendedEnabledParam();
 
 // Returns a string that will cause the search results page to update
 // incrementally. Currently, Instant Extended passes a different param to