Add UMA stats to track whitelist download latency.

components/autofill/browser/autocheckout/whitelist_manager.cc

Index: components/autofill/browser/autocheckout/whitelist_manager.cc
diff --git a/components/autofill/browser/autocheckout/whitelist_manager.cc b/components/autofill/browser/autocheckout/whitelist_manager.cc
index aeb60f113393bfbe12ee93af31708c6632f2588a..5b9891316fb63143f4938b4f03e824c6ce38fa09 100644
--- a/components/autofill/browser/autocheckout/whitelist_manager.cc
+++ b/components/autofill/browser/autocheckout/whitelist_manager.cc
@@ -77,6 +77,8 @@ void WhitelistManager::StartDownloadTimer(size_t interval_seconds) {
 void WhitelistManager::TriggerDownload() {
   callback_is_pending_ = true;
 
+  request_started_timestamp_ = base::Time::Now();
+
   request_.reset(net::URLFetcher::Create(
       0, GURL(kWhitelistUrl), net::URLFetcher::GET, this));
   request_->SetRequestContext(context_getter_);
@@ -99,9 +101,16 @@ void WhitelistManager::OnURLFetchComplete(
   DCHECK_EQ(source, old_request.get());
 
   if (source->GetResponseCode() == net::HTTP_OK) {
+    GetMetricLogger().LogAutocheckoutWhitelistDownloadDuration(
+        base::Time::Now() - request_started_timestamp_,
+        AutofillMetrics::WHITELIST_DOWNLOAD_SUCCEEDED);
     std::string data;
     source->GetResponseAsString(&data);
     BuildWhitelist(data);
+  } else {
+    GetMetricLogger().LogAutocheckoutWhitelistDownloadDuration(
+        base::Time::Now() - request_started_timestamp_,
+        AutofillMetrics::WHITELIST_DOWNLOAD_FAILED);

[Ilya Sherman, 2013/04/17 00:18:01]

nit: Would be nice to move most of this code out of the if/else, and just have a
variable that is set to either AutofillMetrics::WHITELIST_DOWNLOAD_SUCCEEDED or
AutofillMetrics::WHITELIST_DOWNLOAD_FAILED.

[benquan, 2013/04/17 01:51:30]

In the If block, I want to track UMA before calling BuildWhitelist(data), so
that we do not include parsing time. If we want to move the code out of if/else,
it should be before the "if" statement, it will require performing another
(source->GetResponseCode() == net::HTTP_OK) test, it won't be much nicer. I will
leave it as is for now, please let me know if think otherwise.

[Ilya Sherman, 2013/04/17 05:01:48]

You can compute the duration outside of the if/else as well.  IMO that's still
cleaner, but it's not critical to change this.

[benquan, 2013/04/17 05:48:18]

Done.

   }
 
   ScheduleDownload(kDownloadIntervalSeconds);