Adds InstantExtendedEnabledParam to the search request URL iff the query extraction flag is enabled.

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 68ac6d864f792ee1b34f247e58344b83de1ca373..3a340d8c62203429cf4500c1a7334b85efdef3c1 100644
--- a/chrome/browser/search/search.h
+++ b/chrome/browser/search/search.h
@@ -78,6 +78,14 @@ bool IsSuggestPrefEnabled(Profile* profile);
 // the Instant Extended API is not enabled.
 uint64 EmbeddedSearchPageVersion();
 
+// 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);
+
 // Returns whether query extraction is enabled.
 bool IsQueryExtractionEnabled();