--- a/dom/media/DecoderTraits.cpp
+++ b/dom/media/DecoderTraits.cpp
@@ -88,24 +88,16 @@ IsAndroidMediaType(const nsACString& aTy
 
   static const char* supportedTypes[] = {
     "audio/mpeg", "audio/mp4", "video/mp4", "video/x-m4v", nullptr
   };
   return CodecListContains(supportedTypes, aType);
 }
 #endif
 
-#ifdef MOZ_DIRECTSHOW
-static bool
-IsDirectShowSupportedType(const nsACString& aType)
-{
-  return DirectShowDecoder::GetSupportedCodecs(aType, nullptr);
-}
-#endif
-
 /* static */ bool
 DecoderTraits::IsMP4SupportedType(const MediaContentType& aType,
                                   DecoderDoctorDiagnostics* aDiagnostics)
 {
 #ifdef MOZ_FMP4
   return MP4Decoder::IsSupportedType(aType, aDiagnostics);
 #else
   return false;
@@ -170,17 +162,17 @@ CanHandleCodecsType(const MediaContentTy
   }
   if (ADTSDecoder::IsSupportedType(aType)) {
     return CANPLAY_YES;
   }
   if (FlacDecoder::IsSupportedType(aType)) {
     return CANPLAY_YES;
   }
 #ifdef MOZ_DIRECTSHOW
-  DirectShowDecoder::GetSupportedCodecs(aType.Type().AsString(), &codecList);
+  DirectShowDecoder::GetSupportedCodecs(aType, &codecList);
 #endif
 #ifdef MOZ_ANDROID_OMX
   if (MediaDecoder::IsAndroidMediaPluginEnabled()) {
     EnsureAndroidMediaPluginHost()->FindDecoder(aType.Type().AsString(),
                                                 &codecList);
   }
 #endif
   if (!codecList) {
@@ -251,17 +243,17 @@ CanHandleMediaType(const MediaContentTyp
   }
   if (ADTSDecoder::IsSupportedType(mimeType)) {
     return CANPLAY_MAYBE;
   }
   if (FlacDecoder::IsSupportedType(mimeType)) {
     return CANPLAY_MAYBE;
   }
 #ifdef MOZ_DIRECTSHOW
-  if (DirectShowDecoder::GetSupportedCodecs(mimeType.Type().AsString(), nullptr)) {
+  if (DirectShowDecoder::GetSupportedCodecs(mimeType, nullptr)) {
     return CANPLAY_MAYBE;
   }
 #endif
 #ifdef MOZ_ANDROID_OMX
   if (MediaDecoder::IsAndroidMediaPluginEnabled() &&
       EnsureAndroidMediaPluginHost()->FindDecoder(mimeType.Type().AsString(), nullptr)) {
     return CANPLAY_MAYBE;
   }
@@ -357,17 +349,17 @@ InstantiateDecoder(const MediaContentTyp
   if (WebMDecoder::IsSupportedType(aType)) {
     decoder = new WebMDecoder(aOwner);
     return decoder.forget();
   }
 
 #ifdef MOZ_DIRECTSHOW
   // Note: DirectShow should come before WMF, so that we prefer DirectShow's
   // MP3 support over WMF's.
-  if (IsDirectShowSupportedType(aType.Type().AsString())) {
+  if (DirectShowDecoder::GetSupportedCodecs(aType, nullptr)) {
     decoder = new DirectShowDecoder(aOwner);
     return decoder.forget();
   }
 #endif
 
   if (IsHttpLiveStreamingType(aType.Type().AsString())) {
     // We don't have an HLS decoder.
     Telemetry::Accumulate(Telemetry::MEDIA_HLS_DECODER_SUCCESS, false);
@@ -431,17 +423,17 @@ MediaDecoderReader* DecoderTraits::Creat
     decoderReader = new AndroidMediaReader(aDecoder, aType);
   } else
 #endif
   if (WebMDecoder::IsSupportedType(*type)) {
     decoderReader =
       new MediaFormatReader(aDecoder, new WebMDemuxer(aDecoder->GetResource()));
   } else
 #ifdef MOZ_DIRECTSHOW
-  if (IsDirectShowSupportedType(aType)) {
+  if (DirectShowDecoder::GetSupportedCodecs(*type, nullptr)) {
     decoderReader = new DirectShowReader(aDecoder);
   } else
 #endif
   if (false) {} // dummy if to take care of the dangling else
 
   return decoderReader;
 }
 
@@ -469,14 +461,14 @@ bool DecoderTraits::IsSupportedInVideoDo
 #endif
 #ifdef MOZ_FMP4
     MP4Decoder::IsSupportedType(*type, /* DecoderDoctorDiagnostics* */ nullptr) ||
 #endif
     MP3Decoder::IsSupportedType(*type) ||
     ADTSDecoder::IsSupportedType(*type) ||
     FlacDecoder::IsSupportedType(*type) ||
 #ifdef MOZ_DIRECTSHOW
-    IsDirectShowSupportedType(aType) ||
+	  DirectShowDecoder::GetSupportedCodecs(*type, nullptr) ||
 #endif
     false;
 }
 
 } // namespace mozilla

--- a/dom/media/directshow/DirectShowDecoder.cpp
+++ b/dom/media/directshow/DirectShowDecoder.cpp
@@ -2,42 +2,43 @@
 /* vim:set ts=2 sw=2 sts=2 et cindent: */
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * 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 "DirectShowDecoder.h"
 #include "DirectShowReader.h"
 #include "DirectShowUtils.h"
+#include "MediaContentType.h"
 #include "MediaDecoderStateMachine.h"
 #include "mozilla/Preferences.h"
 #include "mozilla/WindowsVersion.h"
 
 namespace mozilla {
 
 MediaDecoderStateMachine* DirectShowDecoder::CreateStateMachine()
 {
   return new MediaDecoderStateMachine(this, new DirectShowReader(this));
 }
 
 /* static */
 bool
-DirectShowDecoder::GetSupportedCodecs(const nsACString& aType,
+DirectShowDecoder::GetSupportedCodecs(const MediaContentType& aType,
                                       char const *const ** aCodecList)
 {
   if (!IsEnabled()) {
     return false;
   }
 
   static char const *const mp3AudioCodecs[] = {
     "mp3",
     nullptr
   };
-  if (aType.EqualsASCII("audio/mpeg") ||
-      aType.EqualsASCII("audio/mp3")) {
+  if (aType.Type() == MEDIAMIMETYPE("audio/mpeg")
+      || aType.Type() == MEDIAMIMETYPE("audio/mp3")) {
     if (aCodecList) {
       *aCodecList = mp3AudioCodecs;
     }
     return true;
   }
 
   return false;
 }

--- a/dom/media/directshow/DirectShowDecoder.h
+++ b/dom/media/directshow/DirectShowDecoder.h
@@ -6,16 +6,18 @@
 
 #if !defined(DirectShowDecoder_h_)
 #define DirectShowDecoder_h_
 
 #include "MediaDecoder.h"
 
 namespace mozilla {
 
+class MediaContentType;
+
 // Decoder that uses DirectShow to playback MP3 files only.
 class DirectShowDecoder : public MediaDecoder
 {
 public:
 
   explicit DirectShowDecoder(MediaDecoderOwner* aOwner);
   virtual ~DirectShowDecoder();
 
@@ -28,17 +30,17 @@ public:
 
   MediaDecoderStateMachine* CreateStateMachine() override;
 
   // Returns true if aType is a MIME type that we render with the
   // DirectShow backend. If aCodecList is non null,
   // it is filled with a (static const) null-terminated list of strings
   // denoting the codecs we'll playback. Note that playback is strictly
   // limited to MP3 only.
-  static bool GetSupportedCodecs(const nsACString& aType,
+  static bool GetSupportedCodecs(const MediaContentType& aType,
                                  char const *const ** aCodecList);
 
   // Returns true if the DirectShow backend is preffed on.
   static bool IsEnabled();
 };
 
 } // namespace mozilla