--- a/dom/media/gtest/TestMediaMIMETypes.cpp
+++ b/dom/media/gtest/TestMediaMIMETypes.cpp
@@ -179,17 +179,19 @@ TEST(MediaMIMETypes, MediaExtendedMIMETy
     bool mEqualsLiteralVideoSlashMp4; // tests `== "video/mp4"`
     bool mHaveCodecs;
   } tests[] =
   { // in                    Type().AsString  app    audio  video ==v/mp4 codecs
     { "video/mp4",           "video/mp4",     false, false, true,  true,  false },
     { "video/mp4; codecs=0", "video/mp4",     false, false, true,  true,  true  },
     { "VIDEO/MP4",           "video/mp4",     false, false, true,  true,  false },
     { "audio/mp4",           "audio/mp4",     false, true,  false, false, false },
-    { "application/x",       "application/x", true, false,  false, false, false }
+    { "video/webm",          "video/webm",    false, false, true,  false, false },
+    { "audio/webm",          "audio/webm",    false, true,  false, false, false },
+    { "application/x",       "application/x", true,  false, false, false, false }
   };
 
   for (const auto& test : tests) {
     Maybe<MediaExtendedMIMEType> type = MakeMediaExtendedMIMEType(test.mTypeString);
     EXPECT_TRUE(type.isSome())
       << "MakeMediaExtendedMIMEType(\"" << test.mTypeString << "\").isSome()";
     EXPECT_TRUE(type->OriginalString().EqualsASCII(test.mTypeString))
       << "MakeMediaExtendedMIMEType(\"" << test.mTypeString << "\")->AsString() == \"" << test.mTypeAsString << "\"";