deleted file mode 100644
--- a/testing/web-platform/meta/media-source/mediasource-append-buffer.html.ini
+++ /dev/null
@@ -1,5 +0,0 @@
-[mediasource-append-buffer.html]
-  type: testharness
-  prefs: [media.mediasource.enabled:true]
-  disabled:
-    if (os == "linux") or (os == "win"): https://bugzilla.mozilla.org/show_bug.cgi?id=1191138

deleted file mode 100644
--- a/testing/web-platform/meta/media-source/mediasource-buffered.html.ini
+++ /dev/null
@@ -1,12 +0,0 @@
-[mediasource-buffered.html]
-  type: testharness
-  prefs: [media.mediasource.enabled:true]
-  [Demuxed content with different lengths]
-    expected:
-      if debug and (os == "win") and (version == "5.1.2600") and (processor == "x86") and (bits == 32): PASS
-      if not debug and (os == "win") and (version == "5.1.2600") and (processor == "x86") and (bits == 32): PASS
-      FAIL
-
-  [Muxed content with different lengths]
-    expected: FAIL
-

deleted file mode 100644
--- a/testing/web-platform/meta/media-source/mediasource-liveseekable.html.ini
+++ /dev/null
@@ -1,26 +0,0 @@
-[mediasource-liveseekable.html]
-  type: testharness
-  [setLiveSeekableRange throws an InvalidStateError exception if a SourceBuffer is updating]
-    expected: FAIL
-
-  [clearLiveSeekableRange throws an InvalidStateError exception if a SourceBuffer is updating]
-    expected: FAIL
-
-  [setLiveSeekableRange throws a TypeError if start is negative]
-    expected: FAIL
-
-  [setLiveSeekableRange throws a TypeError if start is greater than end]
-    expected: FAIL
-
-  [setLiveSeekableRange returns with no error when conditions are correct]
-    expected: FAIL
-
-  [clearLiveSeekableRange returns with no error when conditions are correct]
-    expected: FAIL
-
-  [HTMLMediaElement.seekable returns the live seekable range or an empty range if that range was cleared when nothing is buffered]
-    expected: FAIL
-
-  [HTMLMediaElement.seekable returns the union of the buffered range and the live seekable range, when set]
-    expected: FAIL
-

deleted file mode 100644
--- a/testing/web-platform/meta/media-source/mediasource-preload.html.ini
+++ /dev/null
@@ -1,9 +0,0 @@
-[mediasource-preload.html]
-  type: testharness
-  expected: TIMEOUT
-  [error occurs with bogus blob URL (revoked MediaSource object URL) and element preload=none]
-    expected: TIMEOUT
-
-  [error occurs with bogus blob URL (corrupted MediaSource object URL) and element preload=none]
-    expected: TIMEOUT
-

deleted file mode 100644
--- a/testing/web-platform/meta/media-source/mediasource-remove.html.ini
+++ /dev/null
@@ -1,18 +0,0 @@
-[mediasource-remove.html]
-  type: testharness
-  prefs: [media.mediasource.enabled:true]
-  [Test removing all appended data.]
-    expected:
-      if not ((os == "win") and (version == "5.1.2600")): FAIL
-
-  [Test removing beginning of appended data.]
-    expected:
-      if not ((os == "win") and (version == "5.1.2600")): FAIL
-
-  [Test removing the middle of appended data.]
-    expected:
-      if not ((os == "win") and (version == "5.1.2600")): FAIL
-
-  [Test removing the end of appended data.]
-    expected: FAIL
-

deleted file mode 100644
--- a/testing/web-platform/meta/media-source/mediasource-seek-during-pending-seek.html.ini
+++ /dev/null
@@ -1,4 +0,0 @@
-[mediasource-seek-during-pending-seek.html]
-  type: testharness
-  prefs: [media.mediasource.enabled:true]
-  disabled: https://bugzilla.mozilla.org/show_bug.cgi?id=1183523

deleted file mode 100644
--- a/testing/web-platform/meta/media-source/mediasource-sequencemode-append-buffer.html.ini
+++ /dev/null
@@ -1,12 +0,0 @@
-[mediasource-sequencemode-append-buffer.html]
-  type: testharness
-  prefs: [media.mediasource.enabled:true]
-  [Test sequence AppendMode appendBuffer(first media segment)]
-    expected: FAIL
-
-  [Test sequence AppendMode appendBuffer(second media segment)]
-    expected: FAIL
-
-  [Test sequence AppendMode appendBuffer(second media segment, then first media segment)]
-    expected: FAIL
-