--- a/dom/media/Benchmark.cpp
+++ b/dom/media/Benchmark.cpp
@@ -48,17 +48,17 @@ VP9Benchmark::IsVP9DecodeFast()
 #else
   bool hasPref = Preferences::HasUserValue(sBenchmarkFpsPref);
   uint32_t hadRecentUpdate = Preferences::GetUint(sBenchmarkFpsVersionCheck, 0U);
 
   if (!sHasRunTest && (!hasPref || hadRecentUpdate != sBenchmarkVersionID)) {
     sHasRunTest = true;
 
     RefPtr<WebMDemuxer> demuxer = new WebMDemuxer(
-      new BufferMediaResource(sWebMSample, sizeof(sWebMSample), nullptr));
+      new BufferMediaResource(sWebMSample, sizeof(sWebMSample)));
     RefPtr<Benchmark> estimiser =
       new Benchmark(demuxer,
                     {
                       Preferences::GetInt("media.benchmark.frames", 300), // frames to measure
                       1, // start benchmarking after decoding this frame.
                       8, // loop after decoding that many frames.
                       TimeDuration::FromMilliseconds(
                         Preferences::GetUint("media.benchmark.timeout", 1000))

--- a/dom/media/BufferMediaResource.h
+++ b/dom/media/BufferMediaResource.h
@@ -3,35 +3,31 @@
  * 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/. */
 
 #if !defined(BufferMediaResource_h_)
 #define BufferMediaResource_h_
 
 #include "MediaResource.h"
 #include "nsISeekableStream.h"
-#include "nsIPrincipal.h"
 #include <algorithm>
 
 namespace mozilla {
 
 // A simple MediaResource based on an in memory buffer.  This class accepts
 // the address and the length of the buffer, and simulates a read/seek API
 // on top of it.  The Read implementation involves copying memory, which is
 // unfortunate, but the MediaResource interface mandates that.
 class BufferMediaResource : public MediaResource
 {
 public:
-  BufferMediaResource(const uint8_t* aBuffer,
-                      uint32_t aLength,
-                      nsIPrincipal* aPrincipal)
+  BufferMediaResource(const uint8_t* aBuffer, uint32_t aLength)
     : mBuffer(aBuffer)
     , mLength(aLength)
     , mOffset(0)
-    , mPrincipal(aPrincipal)
   {
   }
 
 protected:
   virtual ~BufferMediaResource()
   {
   }
 
@@ -80,28 +76,26 @@ private:
     aRanges += MediaByteRange(0, int64_t(mLength));
     return NS_OK;
   }
 
   size_t SizeOfExcludingThis(MallocSizeOf aMallocSizeOf) const override
   {
     // Not owned:
     // - mBuffer
-    // - mPrincipal
     size_t size = MediaResource::SizeOfExcludingThis(aMallocSizeOf);
     return size;
   }
 
   size_t SizeOfIncludingThis(MallocSizeOf aMallocSizeOf) const override
   {
     return aMallocSizeOf(this) + SizeOfExcludingThis(aMallocSizeOf);
   }
 
 private:
   const uint8_t * mBuffer;
   uint32_t mLength;
   uint32_t mOffset;
-  nsCOMPtr<nsIPrincipal> mPrincipal;
 };
 
 } // namespace mozilla
 
 #endif

--- a/dom/media/webaudio/MediaBufferDecoder.cpp
+++ b/dom/media/webaudio/MediaBufferDecoder.cpp
@@ -168,27 +168,18 @@ MediaDecodeTask::Run()
   return NS_OK;
 }
 
 bool
 MediaDecodeTask::CreateReader()
 {
   MOZ_ASSERT(NS_IsMainThread());
 
-  nsPIDOMWindowInner* parent = mDecodeJob.mContext->GetParentObject();
-  MOZ_ASSERT(parent);
-
-  nsCOMPtr<nsIPrincipal> principal;
-  nsCOMPtr<nsIScriptObjectPrincipal> sop = do_QueryInterface(parent);
-  if (sop) {
-    principal = sop->GetPrincipal();
-  }
-
   RefPtr<BufferMediaResource> resource =
-    new BufferMediaResource(static_cast<uint8_t*>(mBuffer), mLength, principal);
+    new BufferMediaResource(static_cast<uint8_t*>(mBuffer), mLength);
 
   mMainThread =
     mDecodeJob.mContext->GetOwnerGlobal()->AbstractMainThreadFor(TaskCategory::Other);
 
   // If you change this list to add support for new decoders, please consider
   // updating HTMLMediaElement::CreateDecoder as well.
 
   MediaFormatReaderInit init;