Always allow exact match non-substituting keywords.

chrome/browser/autocomplete/autocomplete.h

 // Copyright (c) 2010 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_AUTOCOMPLETE_AUTOCOMPLETE_H_
 #define CHROME_BROWSER_AUTOCOMPLETE_AUTOCOMPLETE_H_
 #pragma once
 
 #include <string>
 #include <vector>
@@ skipping 555 matching lines @@
   // to explain in the abstract; the practical use case is that after the user
   // deletes text in the edit, the HistoryURLProvider should make sure not to
   // promote a match requiring inline autocomplete too highly.
   //
   // |prefer_keyword| should be true when the keyword UI is onscreen; this will
   // bias the autocomplete result set toward the keyword provider when the input
   // string is a bare keyword.
   //
   // |allow_exact_keyword_match| should be false when triggering keyword mode on
   // the input string would be surprising or wrong, e.g. when highlighting text
-  // in a page and telling the browser to search for it or navigate to it.
+  // in a page and telling the browser to search for it or navigate to it. This
+  // parameter only applies to substituting keywords.
 
   // If |synchronous_only| is true, the controller asks the providers to only
   // return matches which are synchronously available, which should mean that
   // all providers will be done immediately.
   //
   // The controller will fire
   // AUTOCOMPLETE_CONTROLLER_SYNCHRONOUS_MATCHES_AVAILABLE from inside this
   // call, and unless the query is stopped, will fire at least one (and perhaps
   // more) AUTOCOMPLETE_CONTROLLER_RESULT_UPDATED later as more matches come in
   // (even if the query completes synchronously).  Listeners should use the
@@ skipping 130 matching lines @@
   AutocompleteInput::Type input_type;
   // Selected index (if selected) or -1 (AutocompletePopupModel::kNoMatch).
   size_t selected_index;
   // Inline autocompleted length (if displayed).
   size_t inline_autocompleted_length;
   // Result set.
   const AutocompleteResult& result;
 };
 
 #endif  // CHROME_BROWSER_AUTOCOMPLETE_AUTOCOMPLETE_H_