--- a/dom/media/MediaFormatReader.cpp
+++ b/dom/media/MediaFormatReader.cpp
@@ -335,17 +335,17 @@ MediaFormatReader::OnDemuxerInitDone(nsr
 
   mIsEncrypted = crypto && crypto->IsEncrypted();
 
   if (mDecoder && crypto && crypto->IsEncrypted()) {
 #ifdef MOZ_EME
     // Try and dispatch 'encrypted'. Won't go if ready state still HAVE_NOTHING.
     for (uint32_t i = 0; i < crypto->mInitDatas.Length(); i++) {
       NS_DispatchToMainThread(
-        new DispatchKeyNeededEvent(mDecoder, crypto->mInitDatas[i].mInitData, NS_LITERAL_STRING("cenc")));
+        new DispatchKeyNeededEvent(mDecoder, crypto->mInitDatas[i].mInitData, crypto->mInitDatas[i].mType));
     }
 #endif // MOZ_EME
     mInfo.mCrypto = *crypto;
   }
 
   int64_t videoDuration = HasVideo() ? mInfo.mVideo.mDuration : 0;
   int64_t audioDuration = HasAudio() ? mInfo.mAudio.mDuration : 0;
 

--- a/dom/media/VideoUtils.cpp
+++ b/dom/media/VideoUtils.cpp
@@ -485,9 +485,46 @@ IsAACContentType(const nsAString& aConte
     },
     [](const nsAString& codec) {
       return codec.EqualsLiteral("mp4a.40.2") || // MPEG4 AAC-LC
              codec.EqualsLiteral("mp4a.40.5") || // MPEG4 HE-AAC
              codec.EqualsLiteral("mp4a.67");     // MPEG2 AAC-LC
     });
 }
 
+bool
+IsVorbisContentType(const nsAString& aContentType)
+{
+  return CheckContentType(aContentType,
+    [](const nsAString& type) {
+      return type.EqualsLiteral("audio/webm") ||
+             type.EqualsLiteral("audio/ogg");
+    },
+    [](const nsAString& codec) {
+      return codec.EqualsLiteral("vorbis");
+    });
+}
+
+bool
+IsVP8ContentType(const nsAString& aContentType)
+{
+  return CheckContentType(aContentType,
+    [](const nsAString& type) {
+      return type.EqualsLiteral("video/webm");
+    },
+    [](const nsAString& codec) {
+      return codec.EqualsLiteral("vp8");
+    });
+}
+
+bool
+IsVP9ContentType(const nsAString& aContentType)
+{
+  return CheckContentType(aContentType,
+    [](const nsAString& type) {
+      return type.EqualsLiteral("video/webm");
+    },
+    [](const nsAString& codec) {
+      return codec.EqualsLiteral("vp9");
+    });
+}
+
 } // end namespace mozilla

--- a/dom/media/VideoUtils.h
+++ b/dom/media/VideoUtils.h
@@ -442,11 +442,20 @@ StringListContains(const ListString& aLi
   for (const auto& listItem : MakeStringListRange(aList)) {
     if (listItem.Equals(aItem)) {
       return true;
     }
   }
   return false;
 }
 
+bool
+IsVorbisContentType(const nsAString& aContentType);
+
+bool
+IsVP8ContentType(const nsAString& aContentType);
+
+bool
+IsVP9ContentType(const nsAString& aContentType);
+
 } // end namespace mozilla
 
 #endif

--- a/dom/media/eme/MediaKeySystemAccess.cpp
+++ b/dom/media/eme/MediaKeySystemAccess.cpp
@@ -30,16 +30,17 @@
 #include "GMPUtils.h"
 #include "nsAppDirectoryServiceDefs.h"
 #include "nsDirectoryServiceUtils.h"
 #include "nsDirectoryServiceDefs.h"
 #include "nsXULAppAPI.h"
 #include "gmp-audio-decode.h"
 #include "gmp-video-decode.h"
 #include "DecoderDoctorDiagnostics.h"
+#include "WebMDecoder.h"
 
 namespace mozilla {
 namespace dom {
 
 NS_IMPL_CYCLE_COLLECTION_WRAPPERCACHE(MediaKeySystemAccess,
                                       mParent)
 NS_IMPL_CYCLE_COLLECTING_ADDREF(MediaKeySystemAccess)
 NS_IMPL_CYCLE_COLLECTING_RELEASE(MediaKeySystemAccess)
@@ -407,35 +408,100 @@ GMPDecryptsAndGeckoDecodesAAC(mozIGeckoM
     }
     return false;
   }
 #endif
   return MP4Decoder::CanHandleMediaType(aContentType, aDiagnostics);
 }
 
 static bool
+GMPDecryptsAndGeckoDecodesVorbis(mozIGeckoMediaPluginService* aGMPService,
+                                const nsAString& aKeySystem,
+                                const nsAString& aContentType,
+                                DecoderDoctorDiagnostics* aDiagnostics)
+{
+  MOZ_ASSERT(HaveGMPFor(aGMPService,
+             NS_ConvertUTF16toUTF8(aKeySystem),
+             NS_LITERAL_CSTRING(GMP_API_DECRYPTOR)));
+  MOZ_ASSERT(IsVorbisContentType(aContentType));
+  return !HaveGMPFor(aGMPService,
+                     NS_ConvertUTF16toUTF8(aKeySystem),
+                     NS_LITERAL_CSTRING(GMP_API_AUDIO_DECODER),
+                     NS_LITERAL_CSTRING("vorbis")) &&
+         WebMDecoder::CanHandleMediaType(aContentType);
+}
+
+static bool
+GMPDecryptsAndGeckoDecodesVP8(mozIGeckoMediaPluginService* aGMPService,
+                             const nsAString& aKeySystem,
+                             const nsAString& aContentType,
+                             DecoderDoctorDiagnostics* aDiagnostics)
+{
+  MOZ_ASSERT(HaveGMPFor(aGMPService,
+             NS_ConvertUTF16toUTF8(aKeySystem),
+             NS_LITERAL_CSTRING(GMP_API_DECRYPTOR)));
+  MOZ_ASSERT(IsVP8ContentType(aContentType));
+  return !HaveGMPFor(aGMPService,
+                     NS_ConvertUTF16toUTF8(aKeySystem),
+                     NS_LITERAL_CSTRING(GMP_API_VIDEO_DECODER),
+                     NS_LITERAL_CSTRING("vp8")) &&
+         WebMDecoder::CanHandleMediaType(aContentType);
+}
+
+static bool
+GMPDecryptsAndGeckoDecodesVP9(mozIGeckoMediaPluginService* aGMPService,
+                             const nsAString& aKeySystem,
+                             const nsAString& aContentType,
+                             DecoderDoctorDiagnostics* aDiagnostics)
+{
+  MOZ_ASSERT(HaveGMPFor(aGMPService,
+             NS_ConvertUTF16toUTF8(aKeySystem),
+             NS_LITERAL_CSTRING(GMP_API_DECRYPTOR)));
+  MOZ_ASSERT(IsVP9ContentType(aContentType));
+  return !HaveGMPFor(aGMPService,
+                     NS_ConvertUTF16toUTF8(aKeySystem),
+                     NS_LITERAL_CSTRING(GMP_API_VIDEO_DECODER),
+                     NS_LITERAL_CSTRING("vp9")) &&
+         WebMDecoder::CanHandleMediaType(aContentType);
+}
+
+static bool
 IsSupportedAudio(mozIGeckoMediaPluginService* aGMPService,
                  const nsAString& aKeySystem,
                  const nsAString& aAudioType,
                  DecoderDoctorDiagnostics* aDiagnostics)
 {
-  return IsAACContentType(aAudioType) &&
-         (GMPDecryptsAndDecodesAAC(aGMPService, aKeySystem, aDiagnostics) ||
-          GMPDecryptsAndGeckoDecodesAAC(aGMPService, aKeySystem, aAudioType, aDiagnostics));
+  if (IsAACContentType(aAudioType)) {
+    return GMPDecryptsAndDecodesAAC(aGMPService, aKeySystem, aDiagnostics) ||
+           GMPDecryptsAndGeckoDecodesAAC(aGMPService, aKeySystem, aAudioType, aDiagnostics);
+  }
+  if (IsVorbisContentType(aAudioType) && aKeySystem.EqualsLiteral("org.w3.clearkey")) {
+    // GMP does not decode Vorbis, so don't bother checking
+    return GMPDecryptsAndGeckoDecodesVorbis(aGMPService, aKeySystem, aAudioType, aDiagnostics);
+  }
+  return false;
 }
 
 static bool
 IsSupportedVideo(mozIGeckoMediaPluginService* aGMPService,
                  const nsAString& aKeySystem,
                  const nsAString& aVideoType,
                  DecoderDoctorDiagnostics* aDiagnostics)
 {
-  return IsH264ContentType(aVideoType) &&
-         (GMPDecryptsAndDecodesH264(aGMPService, aKeySystem, aDiagnostics) ||
-          GMPDecryptsAndGeckoDecodesH264(aGMPService, aKeySystem, aVideoType, aDiagnostics));
+  if (IsH264ContentType(aVideoType)) {
+    return GMPDecryptsAndDecodesH264(aGMPService, aKeySystem, aDiagnostics) ||
+           GMPDecryptsAndGeckoDecodesH264(aGMPService, aKeySystem, aVideoType, aDiagnostics);
+  }
+  if (IsVP8ContentType(aVideoType) && aKeySystem.EqualsLiteral("org.w3.clearkey")) {
+    return GMPDecryptsAndGeckoDecodesVP8(aGMPService, aKeySystem, aVideoType, aDiagnostics);
+  }
+  if (IsVP9ContentType(aVideoType) && aKeySystem.EqualsLiteral("org.w3.clearkey")) {
+    return GMPDecryptsAndGeckoDecodesVP9(aGMPService, aKeySystem, aVideoType, aDiagnostics);
+  }
+  return false;
 }
 
 static bool
 IsSupported(mozIGeckoMediaPluginService* aGMPService,
             const nsAString& aKeySystem,
             const MediaKeySystemConfiguration& aConfig,
             DecoderDoctorDiagnostics* aDiagnostics)
 {
@@ -469,17 +535,17 @@ IsSupportedInitDataType(const nsString& 
   // All supported keySystems can handle "cenc" initDataType.
   // ClearKey also supports "keyids" and "webm" initDataTypes.
   return aCandidate.EqualsLiteral("cenc") ||
     ((aKeySystem.EqualsLiteral("org.w3.clearkey")
 #ifdef MOZ_WIDEVINE_EME
     || aKeySystem.EqualsLiteral("com.widevine.alpha")
 #endif
     ) &&
-    (aCandidate.EqualsLiteral("keyids") || aCandidate.EqualsLiteral("webm)")));
+    (aCandidate.EqualsLiteral("keyids") || aCandidate.EqualsLiteral("webm")));
 }
 
 static bool
 GetSupportedConfig(mozIGeckoMediaPluginService* aGMPService,
                    const nsAString& aKeySystem,
                    const MediaKeySystemConfiguration& aCandidate,
                    MediaKeySystemConfiguration& aOutConfig,
                    DecoderDoctorDiagnostics* aDiagnostics)

--- a/dom/media/mediasource/TrackBuffersManager.cpp
+++ b/dom/media/mediasource/TrackBuffersManager.cpp
@@ -1045,17 +1045,18 @@ TrackBuffersManager::OnDemuxerInitDone(n
   }
 
   UniquePtr<EncryptionInfo> crypto = mInputDemuxer->GetCrypto();
   if (crypto && crypto->IsEncrypted()) {
 #ifdef MOZ_EME
     // Try and dispatch 'encrypted'. Won't go if ready state still HAVE_NOTHING.
     for (uint32_t i = 0; i < crypto->mInitDatas.Length(); i++) {
       NS_DispatchToMainThread(
-        new DispatchKeyNeededEvent(mParentDecoder, crypto->mInitDatas[i].mInitData, NS_LITERAL_STRING("cenc")));
+        new DispatchKeyNeededEvent(mParentDecoder, crypto->mInitDatas[i].mInitData,
+                                   crypto->mInitDatas[i].mType));
     }
 #endif // MOZ_EME
     info.mCrypto = *crypto;
     // We clear our crypto init data array, so the MediaFormatReader will
     // not emit an encrypted event for the same init data again.
     info.mCrypto.mInitDatas.Clear();
     mEncrypted = true;
   }