--- a/dom/media/MediaContentType.h
+++ b/dom/media/MediaContentType.h
@@ -12,29 +12,36 @@
 #include "nsString.h"
 
 namespace mozilla {
 
 // Class containing media type information for containers.
 class MediaContentType
 {
 public:
+  explicit MediaContentType(const MediaMIMEType& aType)
+    : mExtendedMIMEType(aType)
+  {}
+  explicit MediaContentType(MediaMIMEType&& aType)
+    : mExtendedMIMEType(Move(aType))
+  {}
   explicit MediaContentType(const MediaExtendedMIMEType& aType)
     : mExtendedMIMEType(aType)
   {
   }
   explicit MediaContentType(MediaExtendedMIMEType&& aType)
     : mExtendedMIMEType(Move(aType))
   {
   }
 
+  const MediaMIMEType& Type() const { return mExtendedMIMEType.Type(); }
   const MediaExtendedMIMEType& ExtendedType() const { return mExtendedMIMEType; }
 
   // MIME "type/subtype". Guaranteed not to be empty.
-  const nsACString& GetMIMEType() const { return mExtendedMIMEType.Type(); }
+  const nsACString& GetMIMEType() const { return mExtendedMIMEType.Type().AsString(); }
 
   // Was there an explicit 'codecs' parameter provided?
   bool HaveCodecs() const { return mExtendedMIMEType.HaveCodecs(); }
   // Codecs. May be empty if not provided or explicitly provided as empty.
   const nsAString& GetCodecs() const { return mExtendedMIMEType.GetCodecs(); }
 
   // Sizes and rates.
   Maybe<int32_t> GetWidth() const { return mExtendedMIMEType.GetWidth(); }

--- a/dom/media/MediaMIMETypes.cpp
+++ b/dom/media/MediaMIMETypes.cpp
@@ -5,16 +5,54 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 #include "MediaMIMETypes.h"
 
 #include "nsContentTypeParser.h"
 
 namespace mozilla {
 
+MediaMIMEType::MediaMIMEType(const nsACString& aType)
+  : mMIMEType(aType)
+{
+}
+
+Maybe<MediaMIMEType>
+MakeMediaMIMEType(const nsAString& aType)
+{
+  MOZ_ASSERT(NS_IsMainThread());
+
+  nsContentTypeParser parser(aType);
+  nsAutoString mime;
+  nsresult rv = parser.GetType(mime);
+  if (!NS_SUCCEEDED(rv) || mime.IsEmpty()) {
+    return Nothing();
+  }
+
+  NS_ConvertUTF16toUTF8 mime8{mime};
+
+  return Some(MediaMIMEType(mime8));
+}
+
+Maybe<MediaMIMEType>
+MakeMediaMIMEType(const nsACString& aType)
+{
+  return MakeMediaMIMEType(NS_ConvertUTF8toUTF16(aType));
+}
+
+Maybe<MediaMIMEType>
+MakeMediaMIMEType(const char* aType)
+{
+  if (!aType) {
+    return Nothing();
+  }
+  return MakeMediaMIMEType(nsDependentCString(aType));
+}
+
+
 static int32_t
 GetParameterAsNumber(const nsContentTypeParser& aParser,
                      const char* aParameter,
                      const int32_t aErrorReturn)
 {
   nsAutoString parameterString;
   nsresult rv = aParser.GetParameter(aParameter, parameterString);
   if (NS_FAILED_impl(rv)) {
@@ -27,26 +65,36 @@ GetParameterAsNumber(const nsContentType
   return number;
 }
 
 MediaExtendedMIMEType::MediaExtendedMIMEType(const nsACString& aMIMEType,
                                              bool aHaveCodecs,
                                              const nsAString& aCodecs,
                                              int32_t aWidth, int32_t aHeight,
                                              int32_t aFramerate, int32_t aBitrate)
-  : mMIMEType(Move(aMIMEType))
+  : mMIMEType(aMIMEType)
   , mHaveCodecs(aHaveCodecs)
-  , mCodecs(Move(aCodecs))
+  , mCodecs(aCodecs)
   , mWidth(aWidth)
   , mHeight(aHeight)
   , mFramerate(aFramerate)
   , mBitrate(aBitrate)
 {
 }
 
+MediaExtendedMIMEType::MediaExtendedMIMEType(const MediaMIMEType& aType)
+  : mMIMEType(aType)
+{
+}
+
+MediaExtendedMIMEType::MediaExtendedMIMEType(MediaMIMEType&& aType)
+  : mMIMEType(Move(aType))
+{
+}
+
 Maybe<MediaExtendedMIMEType>
 MakeMediaExtendedMIMEType(const nsAString& aType)
 {
   MOZ_ASSERT(NS_IsMainThread());
 
   nsContentTypeParser parser(aType);
   nsAutoString mime;
   nsresult rv = parser.GetType(mime);

--- a/dom/media/MediaMIMETypes.h
+++ b/dom/media/MediaMIMETypes.h
@@ -7,23 +7,46 @@
 #ifndef MediaMIMETypes_h_
 #define MediaMIMETypes_h_
 
 #include "mozilla/Maybe.h"
 #include "nsString.h"
 
 namespace mozilla {
 
+// Class containing only pre-parsed lowercase media MIME type/subtype.
+class MediaMIMEType
+{
+public:
+  // MIME "type/subtype", always lowercase.
+  const nsACString& AsString() const { return mMIMEType; }
+
+private:
+  friend Maybe<MediaMIMEType> MakeMediaMIMEType(const nsAString& aType);
+  friend class MediaExtendedMIMEType;
+  explicit MediaMIMEType(const nsACString& aType);
+
+  nsCString mMIMEType; // UTF8 MIME "type/subtype".
+};
+
+Maybe<MediaMIMEType> MakeMediaMIMEType(const nsAString& aType);
+Maybe<MediaMIMEType> MakeMediaMIMEType(const nsACString& aType);
+Maybe<MediaMIMEType> MakeMediaMIMEType(const char* aType);
+
+
 // Class containing pre-parsed media MIME type parameters, e.g.:
 // MIME type/subtype, optional codecs, etc.
 class MediaExtendedMIMEType
 {
 public:
+  explicit MediaExtendedMIMEType(const MediaMIMEType& aType);
+  explicit MediaExtendedMIMEType(MediaMIMEType&& aType);
+
   // MIME "type/subtype".
-  const nsACString& Type() const { return mMIMEType; }
+  const MediaMIMEType& Type() const { return mMIMEType; }
 
   // Was there an explicit 'codecs' parameter provided?
   bool HaveCodecs() const { return mHaveCodecs; }
   // Codecs. May be empty if not provided or explicitly provided as empty.
   const nsAString& GetCodecs() const { return mCodecs; }
 
   // Sizes and rates.
   Maybe<int32_t> GetWidth() const { return GetMaybeNumber(mWidth); }
@@ -38,23 +61,23 @@ private:
                         int32_t aWidth, int32_t aHeight,
                         int32_t aFramerate, int32_t aBitrate);
 
   Maybe<int32_t> GetMaybeNumber(int32_t aNumber) const
   {
     return (aNumber < 0) ? Maybe<int32_t>(Nothing()) : Some(int32_t(aNumber));
   }
 
-  nsCString mMIMEType; // UTF8 MIME type.
-  bool mHaveCodecs; // If false, mCodecs must be empty.
+  MediaMIMEType mMIMEType; // MIME type/subtype.
+  bool mHaveCodecs = false; // If false, mCodecs must be empty.
   nsString mCodecs;
-  int32_t mWidth; // -1 if not provided.
-  int32_t mHeight; // -1 if not provided.
-  int32_t mFramerate; // -1 if not provided.
-  int32_t mBitrate; // -1 if not provided.
+  int32_t mWidth = -1; // -1 if not provided.
+  int32_t mHeight = -1; // -1 if not provided.
+  int32_t mFramerate = -1; // -1 if not provided.
+  int32_t mBitrate = -1; // -1 if not provided.
 };
 
 Maybe<MediaExtendedMIMEType> MakeMediaExtendedMIMEType(const nsAString& aType);
 Maybe<MediaExtendedMIMEType> MakeMediaExtendedMIMEType(const nsACString& aType);
 Maybe<MediaExtendedMIMEType> MakeMediaExtendedMIMEType(const char* aType);
 
 } // namespace mozilla