Added UMA stats to track the budget for any service worker which receives a

chrome/browser/push_messaging/push_messaging_browsertest.cc

Index: chrome/browser/push_messaging/push_messaging_browsertest.cc
diff --git a/chrome/browser/push_messaging/push_messaging_browsertest.cc b/chrome/browser/push_messaging/push_messaging_browsertest.cc
index d619fa9939351a04c50d29f966d725e6cb4f1477..8ce4429d2c2e2c2cf4bb36bc4f799c159c0001e5 100644
--- a/chrome/browser/push_messaging/push_messaging_browsertest.cc
+++ b/chrome/browser/push_messaging/push_messaging_browsertest.cc
@@ -15,6 +15,7 @@
 #include "base/message_loop/message_loop.h"
 #include "base/run_loop.h"
 #include "base/strings/utf_string_conversions.h"
+#include "base/test/histogram_tester.h"
 #include "build/build_config.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/browsing_data/browsing_data_helper.h"
@@ -251,10 +252,13 @@ class PushMessagingBrowserTest : public InProcessBrowserTest {
 
   virtual Browser* GetBrowser() const { return browser(); }
 
+  base::HistogramTester* GetHistogramTester() { return &histogram_tester_; }
+
  private:
   std::unique_ptr<net::EmbeddedTestServer> https_server_;
   gcm::FakeGCMProfileService* gcm_service_;
   PushMessagingServiceImpl* push_service_;
+  base::HistogramTester histogram_tester_;
 
 #if defined(ENABLE_NOTIFICATIONS)
   std::unique_ptr<StubNotificationUIManager> notification_manager_;
@@ -739,6 +743,10 @@ IN_PROC_BROWSER_TEST_F(PushMessagingBrowserTest,
   content::WebContents* web_contents =
       GetBrowser()->tab_strip_model()->GetActiveWebContents();
 
+  // Set the site engagement score for the site. Setting it to 4 means it should
+  // have enough budget for two non-shown notification, which cost 2 each.
+  SetSiteEngagementScore(web_contents->GetURL(), 4.0);
+
   // If the site is visible in an active tab, we should not force a notification
   // to be shown. Try it twice, since we allow one mistake per 10 push events.
   gcm::IncomingMessage message;
@@ -757,10 +765,6 @@ IN_PROC_BROWSER_TEST_F(PushMessagingBrowserTest,
       GetBrowser(), GURL("about:blank"), NEW_FOREGROUND_TAB,
       ui_test_utils::BROWSER_TEST_WAIT_FOR_TAB);
 
-  // Set the site engagement score for the site. Setting it to 2 means we should
-  // have enough budget for two non-shown notification.
-  SetSiteEngagementScore(web_contents->GetURL(), 2.0);
-
   // If the Service Worker push event handler shows a notification, we
   // should not show a forced one.
   message.raw_data = "shownotification";
@@ -813,6 +817,37 @@ IN_PROC_BROWSER_TEST_F(PushMessagingBrowserTest,
 
     EXPECT_NE(kPushMessagingForcedNotificationTag, first_notification.tag());
   }
+
+  // Check that the UMA has been recorded correctly.
+  // There should be a total of 7 budget samples, spread across 3 buckets. The
+  // first four notifications (before any budget is consumed) have budget of 4,
+  // which is the starting SES. The next one has 2 (one hidden notification) and
+  // the final two have 0 (two hidden notifications.
+  std::vector<base::Bucket> buckets =
+      GetHistogramTester()->GetAllSamples("PushMessaging.BackgroundBudget");
+  ASSERT_EQ(buckets.size(), 3.0);
+  // First bucket is for 0 budget, which has 2 samples.
+  EXPECT_EQ(buckets[0].min, 0);

[Peter Beverloo, 2016/05/17 11:04:34]

nit: EXPECT_EQ(expected, actual)

Elsewhere and with "assert" as well.

[harkness, 2016/05/17 13:08:16]

Done.

+  EXPECT_EQ(buckets[0].count, 2);
+  // Second bucket is for 2 budget, which has 1 sample.
+  EXPECT_EQ(buckets[1].min, 2);
+  EXPECT_EQ(buckets[1].count, 1);
+  // Final bucket is for 4 budget, which has 4 samples.
+  EXPECT_EQ(buckets[2].min, 4);
+  EXPECT_EQ(buckets[2].count, 4);
+
+  std::vector<base::Bucket> sesForNoBudgetBuckets =

[Peter Beverloo, 2016/05/17 11:04:34]

nit: Chromium style guide wants us to name things like:

site_engagement_score_for_no_budget_buckets (no acronyms, hacker_style)

Which leads me to my next suggestion: let's figure out a shorter name? What
about just "samples" or "buckets" :)

[harkness, 2016/05/17 13:08:16]

Somewhat shortened, but I still kept some context. I don't mind the extra length
in tests to add readability.

+      GetHistogramTester()->GetAllSamples("PushMessaging.SESForNoBudgetOrigin");
+  EXPECT_EQ(sesForNoBudgetBuckets.size(), 1.0);
+  EXPECT_EQ(sesForNoBudgetBuckets[0].min, 4);
+  EXPECT_EQ(sesForNoBudgetBuckets[0].count, 2);
+
+  std::vector<base::Bucket> sesForLowBudgetBuckets =
+      GetHistogramTester()->GetAllSamples(
+          "PushMessaging.SESForLowBudgetOrigin");
+  EXPECT_EQ(sesForLowBudgetBuckets.size(), 1.0);
+  EXPECT_EQ(sesForLowBudgetBuckets[0].min, 4);
+  EXPECT_EQ(sesForLowBudgetBuckets[0].count, 1);
 }
 
 IN_PROC_BROWSER_TEST_F(PushMessagingBrowserTest,