--- a/content/media/webm/nsWebMReader.cpp
+++ b/content/media/webm/nsWebMReader.cpp
@@ -6,17 +6,16 @@
 #include "nsError.h"
 #include "nsBuiltinDecoderStateMachine.h"
 #include "nsBuiltinDecoder.h"
 #include "MediaResource.h"
 #include "nsWebMReader.h"
 #include "nsWebMBufferedParser.h"
 #include "VideoUtils.h"
 #include "nsTimeRanges.h"
-#include "mozilla/Preferences.h"
 
 #define VPX_DONT_DEFINE_STDINT_TYPES
 #include "vpx/vp8dx.h"
 #include "vpx/vpx_decoder.h"
 
 using namespace mozilla;
 using namespace mozilla::layers;
 
@@ -103,27 +102,20 @@ nsWebMReader::nsWebMReader(nsBuiltinDeco
   : nsBuiltinDecoderReader(aDecoder),
   mContext(nsnull),
   mPacketCount(0),
   mChannels(0),
   mVideoTrack(0),
   mAudioTrack(0),
   mAudioStartUsec(-1),
   mAudioFrames(0),
-  mForceStereoMode(0),
   mHasVideo(false),
-  mHasAudio(false),
-  mStereoModeForced(false)
+  mHasAudio(false)
 {
   MOZ_COUNT_CTOR(nsWebMReader);
-
-  mStereoModeForced =
-    NS_SUCCEEDED(Preferences::GetInt(
-          "media.webm.force_stereo_mode",
-          &mForceStereoMode));
 }
 
 nsWebMReader::~nsWebMReader()
 {
   Cleanup();
 
   mVideoPackets.Reset();
   mAudioPackets.Reset();
@@ -279,36 +271,16 @@ nsresult nsWebMReader::ReadMetadata(nsVi
         break;
       case NESTEGG_VIDEO_STEREO_TOP_BOTTOM:
         mInfo.mStereoMode = STEREO_MODE_TOP_BOTTOM;
         break;
       case NESTEGG_VIDEO_STEREO_RIGHT_LEFT:
         mInfo.mStereoMode = STEREO_MODE_RIGHT_LEFT;
         break;
       }
-
-      // Switch only when stereo mode is explicitly set.
-      if (mStereoModeForced) {
-        switch (mForceStereoMode) {
-        case 1:
-          mInfo.mStereoMode = STEREO_MODE_LEFT_RIGHT;
-          break;
-        case 2:
-          mInfo.mStereoMode = STEREO_MODE_RIGHT_LEFT;
-          break;
-        case 3:
-          mInfo.mStereoMode = STEREO_MODE_TOP_BOTTOM;
-          break;
-        case 4:
-          mInfo.mStereoMode = STEREO_MODE_BOTTOM_TOP;
-          break;
-        default:
-          mInfo.mStereoMode = STEREO_MODE_MONO;
-        }
-      }
     }
     else if (!mHasAudio && type == NESTEGG_TRACK_AUDIO) {
       nestegg_audio_params params;
       r = nestegg_track_audio_params(mContext, track, &params);
       if (r == -1) {
         Cleanup();
         return NS_ERROR_FAILURE;
       }

--- a/content/media/webm/nsWebMReader.h
+++ b/content/media/webm/nsWebMReader.h
@@ -202,22 +202,14 @@ private:
 
   // Size of the frame initially present in the stream. The picture region
   // is defined as a ratio relative to this.
   nsIntSize mInitialFrame;
 
   // Picture region, as relative to the initial frame size.
   nsIntRect mPicture;
 
-  // Value of the "media.webm.force_stereo_mode" pref, which we need off the
-  // main thread.
-  PRInt32 mForceStereoMode;
-
   // Booleans to indicate if we have audio and/or video data
   bool mHasVideo;
   bool mHasAudio;
-
-  // Boolean which is set to true when the "media.webm.force_stereo_mode"
-  // pref is explicitly set.
-  bool mStereoModeForced;
 };
 
 #endif