Implement a simple Extension App Omnibox provider.

chrome/browser/autocomplete/autocomplete.h

 // Copyright (c) 2011 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 <map>
 #include <string>
@@ skipping 25 matching lines @@
 // their own thread management when they need to return matches asynchronously.
 //
 // The AutocompleteProviders each return different kinds of matches, such as
 // history or search matches.  These matches are given "relevance" scores.
 // Higher scores are better matches than lower scores.  The relevance scores and
 // classes providing the respective matches are as follows:
 //
 // UNKNOWN input type:
 // --------------------------------------------------------------------|-----
 // Keyword (non-substituting or in keyword UI mode, exact match)       | 1500
+// Extension App (exact match)                                         | 1425
 // HistoryURL (exact or inline autocomplete match)                     | 1400
 // Search Primary Provider (past query in history within 2 days)       | 1399**
 // Search Primary Provider (what you typed)                            | 1300
 // HistoryURL (what you typed)                                         | 1200
+// Extension App (inexact match)                                       | 1175*~
 // Keyword (substituting, exact match)                                 | 1100
 // Search Primary Provider (past query in history older than 2 days)   | 1050--
 // HistoryContents (any match in title of starred page)                | 1000++
 // HistoryURL (inexact match)                                          |  900++
 // Search Primary Provider (navigational suggestion)                   |  800++
 // HistoryContents (any match in title of nonstarred page)             |  700++
 // Search Primary Provider (suggestion)                                |  600++
 // Built-in                                                            |  575++
 // HistoryContents (any match in body of starred page)                 |  550++
 // HistoryContents (any match in body of nonstarred page)              |  500++
 // Keyword (inexact match)                                             |  450
 // Search Secondary Provider (what you typed)                          |  250
 // Search Secondary Provider (past query in history)                   |  200--
 // Search Secondary Provider (navigational suggestion)                 |  150++
 // Search Secondary Provider (suggestion)                              |  100++
 //
 // REQUESTED_URL input type:
 // --------------------------------------------------------------------|-----
 // Keyword (non-substituting or in keyword UI mode, exact match)       | 1500
+// Extension App (exact match)                                         | 1425
 // HistoryURL (exact or inline autocomplete match)                     | 1400
 // Search Primary Provider (past query in history within 2 days)       | 1399**
 // HistoryURL (what you typed)                                         | 1200
+// Extension App (inexact match)                                       | 1175*~
 // Search Primary Provider (what you typed)                            | 1150
 // Keyword (substituting, exact match)                                 | 1100
 // Search Primary Provider (past query in history older than 2 days)   | 1050--
 // HistoryContents (any match in title of starred page)                | 1000++
 // HistoryURL (inexact match)                                          |  900++
 // Search Primary Provider (navigational suggestion)                   |  800++
 // HistoryContents (any match in title of nonstarred page)             |  700++
 // Search Primary Provider (suggestion)                                |  600++
 // Built-in                                                            |  575++
 // HistoryContents (any match in body of starred page)                 |  550++
 // HistoryContents (any match in body of nonstarred page)              |  500++
 // Keyword (inexact match)                                             |  450
 // Search Secondary Provider (what you typed)                          |  250
 // Search Secondary Provider (past query in history)                   |  200--
 // Search Secondary Provider (navigational suggestion)                 |  150++
 // Search Secondary Provider (suggestion)                              |  100++
 //
 // URL input type:
 // --------------------------------------------------------------------|-----
 // Keyword (non-substituting or in keyword UI mode, exact match)       | 1500
+// Extension App (exact match)                                         | 1425
 // HistoryURL (exact or inline autocomplete match)                     | 1400
 // HistoryURL (what you typed)                                         | 1200
+// Extension App (inexact match)                                       | 1175*~
 // Keyword (substituting, exact match)                                 | 1100
 // HistoryURL (inexact match)                                          |  900++
 // Search Primary Provider (what you typed)                            |  850
 // Search Primary Provider (navigational suggestion)                   |  800++
 // Search Primary Provider (past query in history)                     |  750--
 // Keyword (inexact match)                                             |  700
 // Built-in                                                            |  575++
 // Search Primary Provider (suggestion)                                |  300++
 // Search Secondary Provider (what you typed)                          |  250
 // Search Secondary Provider (past query in history)                   |  200--
 // Search Secondary Provider (navigational suggestion)                 |  150++
 // Search Secondary Provider (suggestion)                              |  100++
 //
 // QUERY input type:
 // --------------------------------------------------------------------|-----
 // Keyword (non-substituting or in keyword UI mode, exact match)       | 1500
 // Keyword (substituting, exact match)                                 | 1450
+// Extension App (exact match)                                         | 1425
 // HistoryURL (exact or inline autocomplete match)                     | 1400
 // Search Primary Provider (past query in history within 2 days)       | 1399**
 // Search Primary Provider (what you typed)                            | 1300
+// Extension App (inexact match)                                       | 1175*~
 // Search Primary Provider (past query in history older than 2 days)   | 1050--
 // HistoryContents (any match in title of starred page)                | 1000++
 // HistoryURL (inexact match)                                          |  900++
 // Search Primary Provider (navigational suggestion)                   |  800++
 // HistoryContents (any match in title of nonstarred page)             |  700++
 // Search Primary Provider (suggestion)                                |  600++
 // HistoryContents (any match in body of starred page)                 |  550++
 // HistoryContents (any match in body of nonstarred page)              |  500++
 // Keyword (inexact match)                                             |  450
 // Search Secondary Provider (what you typed)                          |  250
@@ skipping 18 matching lines @@
 //
 // There are two possible providers for search suggestions. If the user has
 // typed a keyword, then the primary provider is the keyword provider and the
 // secondary provider is the default provider. If the user has not typed a
 // keyword, then the primary provider corresponds to the default provider.
 //
 // The value column gives the ranking returned from the various providers.
 // ++: a series of matches with relevance from n up to (n + max_matches).
 // --: relevance score falls off over time (discounted 50 points @ 15 minutes,
 //     450 points @ two weeks)
-// --: relevance score falls off over two days (discounted 99 points after two
+// **: relevance score falls off over two days (discounted 99 points after two
 //     days).
+// *~: Partial matches get a score on a sliding scale from 400-1000 based on
+//     how many times the URL for the Extension App has been typed and how many
+//     of the letters match.
 
 class AutocompleteController;
 class AutocompleteControllerDelegate;
 class AutocompleteInput;
 struct AutocompleteMatch;
 class AutocompleteProvider;
 class AutocompleteResult;
 class HistoryContentsProvider;
 class Profile;
 class SearchProvider;
@@ skipping 554 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_