Adds a UMA histogram to monitor omnibox suggest requests.

chrome/browser/autocomplete/search_provider.h

 // Copyright (c) 2012 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 Search autocomplete provider.  This provider is
 // responsible for all non-keyword autocomplete entries that start with
 // "Search <engine> for ...", including searching for the current input string,
 // search history, and search suggestions.  An instance of it gets created and
 // managed by the autocomplete controller.
 
@@ skipping 300 matching lines @@
                      bool is_keyword,
                      MatchMap* map);
 
   // Returns an AutocompleteMatch for a navigational suggestion.
   AutocompleteMatch NavigationToMatch(const NavigationResult& navigation,
                                       bool is_keyword);
 
   // Updates the value of |done_| from the internal state.
   void UpdateDone();
 
+  // We keep track in a histogram how many suggest requests we send,
+  // how many suggest requests we invalidate (e.g., due to a user typing
+  // another character), and how many replies we receive.
+  enum SuggestRequestsHistogramValue {
+    REQUEST_SENT = 1,
+    REQUEST_INVALIDATED = 2,
+    REPLY_RECEIVED = 3,
+    MAX_SUGGEST_REQUEST_HISTOGRAM_VALUE = 4

[Ilya Sherman, 2012/08/15 23:17:37]

Optional nit: Explicitly specifying "4" here means you'll have to remember to
update it if you ever add more enumerated values.  It's up to you, but I'd leave
it implicit, so that it's harder for the code to get out of sync in the future.

[Mark P, 2012/08/15 23:28:30]

Done.

I thought of this at the time and then forgot to do it.  I think my head isn't
screwed on correctly today.

+  };
+  // Increments the appropriate value in the histogram by one.

[msw, 2012/08/15 23:21:51]

nit: blank line to separate enum/function decls.

[Mark P, 2012/08/15 23:28:30]

Done.

+  static void LogOmniboxSuggestRequest(
+      const SuggestRequestsHistogramValue request_value);

[Ilya Sherman, 2012/08/15 23:17:37]

nit: No need to declare the parameter as const, since it's a primitive type.

[Ilya Sherman, 2012/08/15 23:17:37]

nit: I would move both of these definitions into an anonymous namespace in the
implementation file, unless you need them to be exported to other files
(tests?).

[Mark P, 2012/08/15 23:28:30]

Fixed in process of move to .cc file.

[Mark P, 2012/08/15 23:28:30]

Moved.  (I don't need this function & type exported.)

+
   // Should we query for suggest results immediately? This is normally false,
   // but may be set to true during testing.
   static bool query_suggest_immediately_;
 
   // Maintains the TemplateURLs used.
   Providers providers_;
 
   // The user's input.
   AutocompleteInput input_;
 
@@ skipping 44 matching lines @@
   // Has FinalizeInstantQuery been invoked since the last |Start|?
   bool instant_finalized_;
 
   // The |suggest_text| parameter passed to FinalizeInstantQuery.
   string16 default_provider_suggest_text_;
 
   DISALLOW_COPY_AND_ASSIGN(SearchProvider);
 };
 
 #endif  // CHROME_BROWSER_AUTOCOMPLETE_SEARCH_PROVIDER_H_