Bug 1371205 - MEDIACACHESTREAM_NOTIFIED_LENGTH captures the HTTP header length given to MediaCacheStream - r=cpearce,francois

MozReview-Commit-ID: 9muZcpfD2vG

--HG--
extra : rebase_source : 11de88ac8f0788c3e04ef206bcdacc4ef112a139

dom/media/MediaCache.cpp

@@ -1763,6 +1763,16 @@ MediaCacheStream::NotifyDataLength(int64_t aLength)
 {
   NS_ASSERTION(NS_IsMainThread(), "Only call on main thread");
 
+  if (mStreamLength < 0 && aLength >= 0) {
+    uint32_t length = uint32_t(std::min(aLength, int64_t(UINT32_MAX)));
+    LOG("MediaCacheStream::NotifyDataLength(this=%p) "
+        "MEDIACACHESTREAM_NOTIFIED_LENGTH=%" PRIu32,
+        this,
+        length);
+    Telemetry::Accumulate(
+      Telemetry::HistogramID::MEDIACACHESTREAM_NOTIFIED_LENGTH, length);
+  }
+
   ReentrantMonitorAutoEnter mon(gMediaCache->GetReentrantMonitor());
   mStreamLength = aLength;
 }

toolkit/components/telemetry/Histograms.json

@@ -8442,6 +8442,16 @@
     "n_buckets": 66,
     "description": "MediaCacheStream stream length size in KB; Either known size from the HTTP header if available, or otherwise the size actually downloaded. Recorded at every MediaCacheStream destruction."
   },
+  "MEDIACACHESTREAM_NOTIFIED_LENGTH": {
+    "record_in_processes": ["main", "content"],
+    "alert_emails": ["gsquelart@mozilla.com"],
+    "bug_numbers": [1371205],
+    "expires_in_version": "60",
+    "kind": "linear",
+    "high": 16777216,
+    "n_buckets": 66,
+    "description": "MediaCacheStream stream notified length size in bytes, from the HTTP header. Recorded when each MediaCacheStream is first notified."
+  },
   "VIDEO_MFT_OUTPUT_NULL_SAMPLES": {
     "record_in_processes": ["main", "content"],
     "alert_emails": ["cpearce@mozilla.com"],