Bug 1187760 - Add telemetry to record navigator.requestMediaKeySystemAccess latency. r=edwin,vladan

dom/base/Navigator.cpp

@@ -2841,8 +2841,11 @@ Navigator::RequestMediaKeySystemAccess(const nsAString& aKeySystem,
   EME_LOG(logMsg.get());
 
   nsCOMPtr<nsIGlobalObject> go = do_QueryInterface(mWindow);
-  nsRefPtr<DetailedPromise> promise = DetailedPromise::Create(go, aRv,
-    NS_LITERAL_CSTRING("navigator.requestMediaKeySystemAccess"));
+  nsRefPtr<DetailedPromise> promise =
+    DetailedPromise::Create(go, aRv,
+      NS_LITERAL_CSTRING("navigator.requestMediaKeySystemAccess"),
+      Telemetry::VIDEO_EME_REQUEST_SUCCESS_LATENCY_MS,
+      Telemetry::VIDEO_EME_REQUEST_FAILURE_LATENCY_MS);
   if (aRv.Failed()) {
     return nullptr;
   }

dom/media/eme/DetailedPromise.cpp

@@ -16,12 +16,24 @@ DetailedPromise::DetailedPromise(nsIGlobalObject* aGlobal,
   : Promise(aGlobal)
   , mName(aName)
   , mResponded(false)
+  , mStartTime(TimeStamp::Now())
 {
 }
 
+DetailedPromise::DetailedPromise(nsIGlobalObject* aGlobal,
+                                 const nsACString& aName,
+                                 Telemetry::ID aSuccessLatencyProbe,
+                                 Telemetry::ID aFailureLatencyProbe)
+  : DetailedPromise(aGlobal, aName)
+{
+  mSuccessLatencyProbe.Construct(aSuccessLatencyProbe);
+  mFailureLatencyProbe.Construct(aFailureLatencyProbe);
+}
+
 DetailedPromise::~DetailedPromise()
 {
   MOZ_ASSERT(mResponded == IsPending());
+  MaybeReportTelemetry(Failed);
 }
 
 void
@@ -31,7 +43,7 @@ DetailedPromise::MaybeReject(nsresult aArg, const nsACString& aReason)
                       PromiseFlatCString(aReason).get());
   EME_LOG(msg.get());
 
-  mResponded = true;
+  MaybeReportTelemetry(Failed);
 
   LogToBrowserConsole(NS_ConvertUTF8toUTF16(msg));
 
@@ -56,5 +68,35 @@ DetailedPromise::Create(nsIGlobalObject* aGlobal,
   return aRv.Failed() ? nullptr : promise.forget();
 }
 
+/* static */ already_AddRefed<DetailedPromise>
+DetailedPromise::Create(nsIGlobalObject* aGlobal,
+                        ErrorResult& aRv,
+                        const nsACString& aName,
+                        Telemetry::ID aSuccessLatencyProbe,
+                        Telemetry::ID aFailureLatencyProbe)
+{
+  nsRefPtr<DetailedPromise> promise = new DetailedPromise(aGlobal, aName, aSuccessLatencyProbe, aFailureLatencyProbe);
+  promise->CreateWrapper(nullptr, aRv);
+  return aRv.Failed() ? nullptr : promise.forget();
+}
+
+void
+DetailedPromise::MaybeReportTelemetry(Status aStatus)
+{
+  if (mResponded) {
+    return;
+  }
+  mResponded = true;
+  if (!mSuccessLatencyProbe.WasPassed() || !mFailureLatencyProbe.WasPassed()) {
+    return;
+  }
+  uint32_t latency = (TimeStamp::Now() - mStartTime).ToMilliseconds();
+  EME_LOG("%s %s latency %ums reported via telemetry", mName.get(),
+          ((aStatus == Succeeded) ? "succcess" : "failure"), latency);
+  Telemetry::ID tid = (aStatus == Succeeded) ? mSuccessLatencyProbe.Value()
+                                             : mFailureLatencyProbe.Value();
+  Telemetry::Accumulate(tid, latency);
+}
+
 } // namespace dom
 } // namespace mozilla

dom/media/eme/DetailedPromise.h

@@ -8,6 +8,7 @@
 #define __DetailedPromise_h__
 
 #include "mozilla/dom/Promise.h"
+#include "mozilla/Telemetry.h"
 #include "EMEUtils.h"
 
 namespace mozilla {
@@ -22,13 +23,21 @@ class DetailedPromise : public Promise
 {
 public:
   static already_AddRefed<DetailedPromise>
-  Create(nsIGlobalObject* aGlobal, ErrorResult& aRv, const nsACString& aName);
+  Create(nsIGlobalObject* aGlobal,
+         ErrorResult& aRv,
+         const nsACString& aName);
+
+  static already_AddRefed<DetailedPromise>
+  Create(nsIGlobalObject* aGlobal, ErrorResult& aRv,
+         const nsACString& aName,
+         Telemetry::ID aSuccessLatencyProbe,
+         Telemetry::ID aFailureLatencyProbe);
 
   template <typename T>
   void MaybeResolve(const T& aArg)
   {
     EME_LOG("%s promise resolved", mName.get());
-    mResponded = true;
+    MaybeReportTelemetry(Succeeded);
     Promise::MaybeResolve<T>(aArg);
   }
 
@@ -39,11 +48,23 @@ public:
   void MaybeReject(ErrorResult&, const nsACString& aReason);
 
 private:
-  explicit DetailedPromise(nsIGlobalObject* aGlobal, const nsACString& aName);
+  explicit DetailedPromise(nsIGlobalObject* aGlobal,
+                           const nsACString& aName);
+
+  explicit DetailedPromise(nsIGlobalObject* aGlobal,
+                           const nsACString& aName,
+                           Telemetry::ID aSuccessLatencyProbe,
+                           Telemetry::ID aFailureLatencyProbe);
   virtual ~DetailedPromise();
 
+  enum Status { Succeeded, Failed };
+  void MaybeReportTelemetry(Status aStatus);
+
   nsCString mName;
   bool mResponded;
+  TimeStamp mStartTime;
+  Optional<Telemetry::ID> mSuccessLatencyProbe;
+  Optional<Telemetry::ID> mFailureLatencyProbe;
 };
 
 } // namespace dom

toolkit/components/telemetry/Histograms.json

@@ -9383,6 +9383,24 @@
     "releaseChannelCollection": "opt-out",
     "description": "Reason for reporting the Adobe CDM to be unsupported. (1 = NOT_WINDOWS; 2 = WINDOWS_VERSION)"
   },
+  "VIDEO_EME_REQUEST_SUCCESS_LATENCY_MS": {
+    "alert_emails": ["cpearce@mozilla.com"],
+    "expires_in_version": "50",
+    "kind": "exponential",
+    "high": "60000",
+    "n_buckets": 60,
+    "releaseChannelCollection": "opt-out",
+    "description": "Time spent waiting for a navigator.requestMediaKeySystemAccess call to succeed."
+  },
+  "VIDEO_EME_REQUEST_FAILURE_LATENCY_MS": {
+    "alert_emails": ["cpearce@mozilla.com"],
+    "expires_in_version": "50",
+    "kind": "exponential",
+    "high": "60000",
+    "n_buckets": 60,
+    "releaseChannelCollection": "opt-out",
+    "description": "Time spent waiting for a navigator.requestMediaKeySystemAccess call to fail."
+  },
   "FXA_CONFIGURED": {
     "alert_emails": ["fx-team@mozilla.com"],
     "expires_in_version": "45",