Adds a UMA histogram to monitor omnibox suggest requests.

chrome/browser/autocomplete/search_provider.cc

 // 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.
 
 #include "chrome/browser/autocomplete/search_provider.h"
 
 #include <algorithm>
 #include <cmath>
 
 #include "base/callback.h"
@@ skipping 275 matching lines @@
 };
 
 void SearchProvider::Run() {
   // Start a new request with the current input.
   DCHECK(!done_);
   suggest_results_pending_ = 0;
   time_suggest_request_sent_ = base::TimeTicks::Now();
   const TemplateURL* default_url = providers_.GetDefaultProviderURL();
   if (default_url && !default_url->suggestions_url().empty()) {
     suggest_results_pending_++;
+    // Increment bucket 1 in the histogram (number of requests sent).
+    UMA_HISTOGRAM_ENUMERATION("Omnibox.SuggestRequests", 1, 4);
     default_fetcher_.reset(CreateSuggestFetcher(kDefaultProviderURLFetcherID,
         default_url->suggestions_url_ref(), input_.text()));
   }
   const TemplateURL* keyword_url = providers_.GetKeywordProviderURL();
   if (keyword_url && !keyword_url->suggestions_url().empty()) {
     suggest_results_pending_++;
+    // Increment bucket 1 in the histogram (number of requests sent).
+    UMA_HISTOGRAM_ENUMERATION("Omnibox.SuggestRequests", 1, 4);

[Ilya Sherman, 2012/08/15 22:42:06]

To avoid problems from typos and such, there are two best practices for
enumerated histograms:

(1) Only declare the UMA_HISTOGRAM_ENUMERATION macro in a single location for
each distinct histogram.  This usually involves defining a helper function like
LogOmniboxSuggestRequest().  This makes it much harder to name the histogram
differently in different places due to a typo.  (This applies to all histograms,
not just enumerated ones; but many of the other histograms more naturally appear
in just one place in the code.)

(2) Use an actual C++ enumeration to name the constants corresponding to "1" and
"4".  This both helps with readability, makes typos and copy/paste errors more
obvious, and makes it easier to extend the list of enumerated values later
(since you don't have to remember to change the "4" in the macro).

Also, is there any particular reason why you're avoiding use of bucket 0?

[Mark P, 2012/08/15 23:09:46]

Good idea.  Done.
Another good idea.  Done.
I don't like the idea of exploiting the underflow bucket to count things.

     keyword_fetcher_.reset(CreateSuggestFetcher(kKeywordProviderURLFetcherID,
         keyword_url->suggestions_url_ref(), keyword_input_text_));
   }
 
   // Both the above can fail if the providers have been modified or deleted
   // since the query began.
   if (suggest_results_pending_ == 0) {
     UpdateDone();
     // We only need to update the listener if we're actually done.
     if (done_)
@@ skipping 13 matching lines @@
 void SearchProvider::AddProviderInfo(ProvidersInfo* provider_info) const {
   provider_info->push_back(metrics::OmniboxEventProto_ProviderInfo());
   metrics::OmniboxEventProto_ProviderInfo& new_entry = provider_info->back();
   new_entry.set_provider(AsOmniboxEventProviderType());
   new_entry.set_provider_done(done_);
 }
 
 void SearchProvider::OnURLFetchComplete(const net::URLFetcher* source) {
   DCHECK(!done_);
   suggest_results_pending_--;
+  // Increment bucket 3 in the histogram (number of requests for which
+  // we received a response).
+  UMA_HISTOGRAM_ENUMERATION("Omnibox.SuggestRequests", 3, 4);
   DCHECK_GE(suggest_results_pending_, 0);  // Should never go negative.
   const net::HttpResponseHeaders* const response_headers =
       source->GetResponseHeaders();
   std::string json_data;
   source->GetResponseAsString(&json_data);
   // JSON is supposed to be UTF-8, but some suggest service providers send JSON
   // files in non-UTF-8 encodings.  The actual encoding is usually specified in
   // the Content-Type header field.
   if (response_headers) {
     std::string charset;
@@ skipping 197 matching lines @@
   // because they are visible when the TCP connection is established, but the
   // specific path may reveal private information.
   if (LowerCaseEqualsASCII(input_.scheme(), chrome::kHttpsScheme) &&
       parts.path.is_nonempty())
     return false;
 
   return true;
 }
 
 void SearchProvider::StopSuggest() {
+  // Increment bucket 2 in the histogram by the number of requests pending
+  // that were invalidated.
+  for (int i = 0; i < suggest_results_pending_; i++)
+    UMA_HISTOGRAM_ENUMERATION("Omnibox.SuggestRequests", 2, 4);
   suggest_results_pending_ = 0;
   timer_.Stop();
   // Stop any in-progress URL fetches.
   keyword_fetcher_.reset();
   default_fetcher_.reset();
 }
 
 void SearchProvider::ClearResults() {
   keyword_suggest_results_.clear();
   default_suggest_results_.clear();
@@ skipping 650 matching lines @@
       ACMatchClassification::NONE, &match.description_class);
   return match;
 }
 
 void SearchProvider::UpdateDone() {
   // We're done when there are no more suggest queries pending (this is set to 1
   // when the timer is started) and we're not waiting on instant.
   done_ = ((suggest_results_pending_ == 0) &&
            (instant_finalized_ || !InstantController::IsEnabled(profile_)));
 }