Adds a UMA histogram to monitor omnibox suggest requests.

chrome/browser/autocomplete/search_provider.h

Index: chrome/browser/autocomplete/search_provider.h
diff --git a/chrome/browser/autocomplete/search_provider.h b/chrome/browser/autocomplete/search_provider.h
index 50631579c5f06660607687e6e643e86361431ce1..523628e4c779055aae5cd2faa7a4ce74ba3d65a6 100644
--- a/chrome/browser/autocomplete/search_provider.h
+++ b/chrome/browser/autocomplete/search_provider.h
@@ -318,6 +318,19 @@ class SearchProvider : public AutocompleteProvider,
   // 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_;