First pass at experimental omnibox API. There are plenty of rough edges and

chrome/browser/autocomplete/keyword_provider.h

-// Copyright (c) 2009 The Chromium Authors. All rights reserved.
+// 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.
 //
 // This file contains the keyword autocomplete provider. The keyword provider
 // is responsible for remembering/suggesting user "search keyword queries"
 // (e.g.  "imdb Godzilla") and then fixing them up into valid URLs.  An
 // instance of it gets created and managed by the autocomplete controller.
 // KeywordProvider uses a TemplateURLModel to find the set of keywords.
 //
 // For more information on the autocomplete system in general, including how
 // the autocomplete controller and autocomplete providers work, see
 // chrome/browser/autocomplete.h.
 
 #ifndef CHROME_BROWSER_AUTOCOMPLETE_KEYWORD_PROVIDER_H_
 #define CHROME_BROWSER_AUTOCOMPLETE_KEYWORD_PROVIDER_H_
 
 #include <string>
 
 #include "chrome/browser/autocomplete/autocomplete.h"
+#include "chrome/common/notification_registrar.h"
 
 class Profile;
 class TemplateURL;
 class TemplateURLModel;
 
 // Autocomplete provider for keyword input.
 //
 // After construction, the autocomplete controller repeatedly calls Start()
 // with some user input, each time expecting to receive a small set of the best
 // matches (either synchronously or asynchronously).
 //
 // To construct these matches, the provider treats user input as a series of
 // whitespace-delimited tokens and tries to match the first token as the prefix
 // of a known "keyword".  A keyword is some string that maps to a search query
 // URL; the rest of the user's input is taken as the input to the query.  For
 // example, the keyword "bug" might map to the URL "http://b/issue?id=%s", so
 // input like "bug 123" would become "http://b/issue?id=123".
 //
 // Because we do prefix matching, user input could match more than one keyword
 // at once.  (Example: the input "f jazz" matches all keywords starting with
 // "f".)  We return the best matches, up to three.
 //
 // The resulting matches are shown with content specified by the keyword
 // (usually "Search [name] for %s"), description "(Keyword: [keyword])", and
 // action "[keyword] %s".  If the user has typed a (possibly partial) keyword
 // but no search terms, the suggested result is shown greyed out, with
 // "<enter term(s)>" as the substituted input, and does nothing when selected.
-class KeywordProvider : public AutocompleteProvider {
+class KeywordProvider :
+    public AutocompleteProvider,
+    public NotificationObserver {
  public:
   KeywordProvider(ACProviderListener* listener, Profile* profile);
   // For testing.
   KeywordProvider(ACProviderListener* listener, TemplateURLModel* model);
 
   // Returns the replacement string from the user input. The replacement
   // string is the portion of the input that does not contain the keyword.
   // For example, the replacement string for "b blah" is blah.
   static std::wstring SplitReplacementStringFromInput(
       const std::wstring& input);
@@ skipping 37 matching lines @@
 
   // Determines the relevance for some input, given its type, whether the user
   // typed the complete keyword, and whether the keyword needs query text (true
   // if the keyword supports replacement and the user isn't in "prefer keyword
   // matches" mode).
   static int CalculateRelevance(AutocompleteInput::Type type,
                                 bool complete,
                                 bool no_query_text_needed);
 
   // Creates a fully marked-up AutocompleteMatch from the user's input.
+  // If |relevance| is negative, calculate a relevance based on heuristics.
   AutocompleteMatch CreateAutocompleteMatch(
       TemplateURLModel* model,
       const std::wstring keyword,
       const AutocompleteInput& input,
       size_t prefix_length,
-      const std::wstring& remaining_input);
+      const std::wstring& remaining_input,
+      int relevance);
+
+  // NotificationObserver interface.
+  void Observe(NotificationType type,
+               const NotificationSource& source,
+               const NotificationDetails& details);
 
   // Model for the keywords.  This is only non-null when testing, otherwise the
   // TemplateURLModel from the Profile is used.
   TemplateURLModel* model_;
 
+  // Identifies the current input state. This is incremented each time the
+  // autocomplete edit's input changes in any way. It is used to tell whether
+  // suggest results from the extension are current.
+  int current_input_id_;
+
+  // The input state at the time we last asked the extension for suggest
+  // results.
+  AutocompleteInput extension_suggest_last_input_;
+
+  // We remember the last suggestions we've received from the extension in case
+  // we need to reset our matches without asking the extension again.
+  std::vector<AutocompleteMatch> extension_suggest_matches_;
+
+  NotificationRegistrar registrar_;
+
   DISALLOW_EVIL_CONSTRUCTORS(KeywordProvider);
 };
 
 #endif  // CHROME_BROWSER_AUTOCOMPLETE_KEYWORD_PROVIDER_H_