--- a/dom/media/DecoderTraits.cpp
+++ b/dom/media/DecoderTraits.cpp
@@ -4,16 +4,17 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 #include "DecoderTraits.h"
 #include "MediaDecoder.h"
 #include "nsCharSeparatedTokenizer.h"
 #include "nsMimeTypes.h"
 #include "mozilla/Preferences.h"
+#include "mozilla/Telemetry.h"
 
 #include "OggDecoder.h"
 #include "OggReader.h"
 
 #include "WebMDecoder.h"
 #include "WebMDemuxer.h"
 
 #ifdef MOZ_RAW
@@ -167,16 +168,31 @@ DecoderTraits::IsWebMTypeAndEnabled(cons
 }
 
 /* static */ bool
 DecoderTraits::IsWebMAudioType(const nsACString& aType)
 {
   return aType.EqualsASCII("audio/webm");
 }
 
+static char const *const gHttpLiveStreamingTypes[] = {
+  // For m3u8.
+  // https://tools.ietf.org/html/draft-pantos-http-live-streaming-19#section-10
+  "application/vnd.apple.mpegurl",
+  // Some sites serve these as the informal m3u type.
+  "audio/x-mpegurl",
+  nullptr
+};
+
+static bool
+IsHttpLiveStreamingType(const nsACString& aType)
+{
+  return CodecListContains(gHttpLiveStreamingTypes, aType);
+}
+
 #ifdef MOZ_OMX_DECODER
 static const char* const gOmxTypes[] = {
   "audio/mpeg",
   "audio/mp4",
   "audio/amr",
   "audio/3gpp",
   "audio/flac",
   "video/mp4",
@@ -466,16 +482,20 @@ DecoderTraits::CanHandleCodecsType(const
 /* static */
 CanPlayStatus
 DecoderTraits::CanHandleMediaType(const char* aMIMEType,
                                   bool aHaveRequestedCodecs,
                                   const nsAString& aRequestedCodecs)
 {
   MOZ_ASSERT(NS_IsMainThread());
 
+  if (IsHttpLiveStreamingType(nsDependentCString(aMIMEType))) {
+    Telemetry::Accumulate(Telemetry::MEDIA_HLS_CANPLAY_REQUESTED, true);
+  }
+
   if (aHaveRequestedCodecs) {
     CanPlayStatus result = CanHandleCodecsType(aMIMEType, aRequestedCodecs);
     if (result == CANPLAY_NO || result == CANPLAY_YES) {
       return result;
     }
   }
 #ifdef MOZ_RAW
   if (IsRawType(nsDependentCString(aMIMEType))) {
@@ -606,16 +626,21 @@ InstantiateDecoder(const nsACString& aTy
   // Note: DirectShow should come before WMF, so that we prefer DirectShow's
   // MP3 support over WMF's.
   if (IsDirectShowSupportedType(aType)) {
     decoder = new DirectShowDecoder(aOwner);
     return decoder.forget();
   }
 #endif
 
+  if (IsHttpLiveStreamingType(aType)) {
+    // We don't have an HLS decoder.
+    Telemetry::Accumulate(Telemetry::MEDIA_HLS_DECODER_SUCCESS, false);
+  }
+
   return nullptr;
 }
 
 /* static */
 already_AddRefed<MediaDecoder>
 DecoderTraits::CreateDecoder(const nsACString& aType, MediaDecoderOwner* aOwner)
 {
   MOZ_ASSERT(NS_IsMainThread());

--- a/toolkit/components/telemetry/Histograms.json
+++ b/toolkit/components/telemetry/Histograms.json
@@ -6221,16 +6221,31 @@
   },
   "MEDIA_OGG_LOADED_IS_CHAINED": {
     "alert_emails": ["cpearce@mozilla.com"],
     "expires_in_version": "53",
     "kind": "boolean",
     "description": "Whether Ogg audio/video encountered are chained or not.",
     "bug_numbers": [1230295]
   },
+  "MEDIA_HLS_CANPLAY_REQUESTED": {
+    "alert_emails": ["ajones@mozilla.com", "giles@mozilla.com"],
+    "expires_in_version": "50",
+    "kind": "boolean",
+    "description": "Reports a true value when a page requests canPlayType for an HTTP Live Streaming media type (or generic m3u playlist).",
+    "bug_numbers": [1262659]
+  },
+  "MEDIA_HLS_DECODER_SUCCESS": {
+    "alert_emails": ["ajones@mozilla.com", "giles@mozilla.com"],
+    "expires_in_version": "50",
+    "kind": "boolean",
+    "description": "Reports whether a decoder for an HTTP Live Streaming media type was created when requested.",
+    "bug_numbers": [1262659]
+
+  },
   "VIDEO_MFT_OUTPUT_NULL_SAMPLES": {
     "alert_emails": ["cpearce@mozilla.com"],
     "expires_in_version": "53",
     "kind": "enumerated",
     "n_values": 10,
     "description": "Does the WMF video decoder return success but null output? 0 = playback successful, 1 = excessive null output but able to decode some frames, 2 = excessive null output and gave up, 3 = null output but recovered, 4 = non-excessive null output without being able to decode frames.",
     "bug_numbers": [1176071]
   },