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

chrome/browser/push_messaging/background_budget_service.cc

Index: chrome/browser/push_messaging/background_budget_service.cc
diff --git a/chrome/browser/push_messaging/background_budget_service.cc b/chrome/browser/push_messaging/background_budget_service.cc
index 5963bc288873b2ae56b54911f30177f9bb108c42..dd7ca4750720866bd1bfb013d7e13a07055fcf50 100644
--- a/chrome/browser/push_messaging/background_budget_service.cc
+++ b/chrome/browser/push_messaging/background_budget_service.cc
@@ -8,6 +8,7 @@
 
 #include "base/callback.h"
 #include "base/memory/ptr_util.h"
+#include "base/metrics/histogram_macros.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_split.h"
 #include "base/strings/stringprintf.h"
@@ -24,10 +25,15 @@
 namespace {
 
 constexpr char kSeparator = '#';
-// We calculate the ratio of the different components of a budget with respect
+
+// Calculate the ratio of the different components of a budget with respect
 // to a maximum time period of 10 days = 864000.0 seconds.
 constexpr double kSecondsToAccumulate = 864000.0;
 
+// Currently this just costs 2.0, but it may expand to include things like
+// whether wifi is available in the mobile case.
+const double kBackgroundProcessingCost = 2.0;

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

What's your take on explicitly calling out that this is the budget for
notifications, rather than "background processing" in general? (Similar to
SiteEngagementScore::Get*Points().)

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

I've split it out now, although it makes the SES recording for no/low budget a
bit weird if there could be different costs. However, that will be an issue
we'll have to deal with when we go with the tri state anyway.

+
 bool GetBudgetDataFromPrefs(Profile* profile,
                             const GURL& origin,
                             double* old_budget,
@@ -80,6 +86,14 @@ void SetBudgetDataInPrefs(Profile* profile,
   map->SetStringWithoutPathExpansion(origin.spec(), s);
 }
 
+void RecordSESForNoBudgetOrigin(double ses) {
+  UMA_HISTOGRAM_COUNTS("PushMessaging.SESForNoBudgetOrigin", ses);
+}
+
+void RecordSESForLowBudgetOrigin(double ses) {
+  UMA_HISTOGRAM_COUNTS("PushMessaging.SESForLowBudgetOrigin", ses);

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

Can we just inline these calls? No need for them to have their own methods,
since they're only used once.

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

Done.

+}
+
 }  // namespace
 
 BackgroundBudgetService::BackgroundBudgetService(Profile* profile)
@@ -95,6 +109,11 @@ void BackgroundBudgetService::RegisterProfilePrefs(
   registry->RegisterDictionaryPref(prefs::kBackgroundBudgetMap);
 }
 
+// static
+double BackgroundBudgetService::GetBackgroundProcessingCost() {
+  return kBackgroundProcessingCost;
+}
+
 double BackgroundBudgetService::GetBudget(const GURL& origin) {
   DCHECK_EQ(origin, origin.GetOrigin());
 
@@ -136,6 +155,14 @@ double BackgroundBudgetService::GetBudget(const GURL& origin) {
   // component, which gives extra budget to sites that have a high ses score.
   double budget = budget_carryover + ses_component;
   DCHECK_GE(budget, 0.0);
+
+  // Generate histograms for the GetBudget calls which would return "no budget"
+  // or "low budget" if an API was available to app developers.
+  if (budget < GetBackgroundProcessingCost())
+    RecordSESForNoBudgetOrigin(ses_score);
+  else if (budget < 2.0 * GetBackgroundProcessingCost())
+    RecordSESForLowBudgetOrigin(ses_score);
+
   return budget;
 }