--- a/content/media/mediasource/MediaSource.cpp
+++ b/content/media/mediasource/MediaSource.cpp
@@ -23,16 +23,21 @@
 #include "nsError.h"
 #include "nsIEventTarget.h"
 #include "nsIRunnable.h"
 #include "nsPIDOMWindow.h"
 #include "nsString.h"
 #include "nsThreadUtils.h"
 #include "prlog.h"
 
+#if defined(DEBUG)
+#include <sys/stat.h>
+#include <sys/types.h>
+#endif
+
 struct JSContext;
 class JSObject;
 
 #ifdef PR_LOGGING
 PRLogModuleInfo* GetMediaSourceLog()
 {
   static PRLogModuleInfo* sLogModule;
   if (!sLogModule) {
@@ -502,16 +507,30 @@ MediaSource::InitializationEvent()
 {
   MOZ_ASSERT(NS_IsMainThread());
   MSE_DEBUG("MediaSource(%p)::InitializationEvent()", this);
   if (mDecoder) {
     mDecoder->PrepareReaderInitialization();
   }
 }
 
+#if defined(DEBUG)
+void
+MediaSource::Dump(const char* aPath)
+{
+  char buf[255];
+  PR_snprintf(buf, sizeof(buf), "%s/mediasource-%p", aPath, this);
+  mkdir(buf, 0700);
+
+  if (mSourceBuffers) {
+    mSourceBuffers->Dump(buf);
+  }
+}
+#endif
+
 nsPIDOMWindow*
 MediaSource::GetParentObject() const
 {
   return GetOwner();
 }
 
 JSObject*
 MediaSource::WrapObject(JSContext* aCx)

--- a/content/media/mediasource/MediaSource.h
+++ b/content/media/mediasource/MediaSource.h
@@ -93,16 +93,22 @@ public:
   // Queue InitializationEvent to run on the main thread.  Called when a
   // SourceBuffer has an initialization segment appended, but only
   // dispatched the first time (using mFirstSourceBufferInitialization).
   // Demarcates the point in time at which only currently registered
   // TrackBuffers are treated as essential by the MediaSourceReader for
   // initialization.
   void QueueInitializationEvent();
 
+#if defined(DEBUG)
+  // Dump the contents of each SourceBuffer to a series of files under aPath.
+  // aPath must exist.  Debug only, invoke from your favourite debugger.
+  void Dump(const char* aPath);
+#endif
+
 private:
   ~MediaSource();
 
   explicit MediaSource(nsPIDOMWindow* aWindow);
 
   friend class AsyncEventRunner<MediaSource>;
   void DispatchSimpleEvent(const char* aName);
   void QueueAsyncSimpleEvent(const char* aName);

--- a/content/media/mediasource/ResourceQueue.h
+++ b/content/media/mediasource/ResourceQueue.h
@@ -129,16 +129,33 @@ public:
     for (uint32_t i = 0; i < uint32_t(GetSize()); ++i) {
       const ResourceItem* item = ResourceAt(i);
       size += item->SizeOfIncludingThis(aMallocSizeOf);
     }
 
     return size;
   }
 
+#if defined(DEBUG)
+  void Dump(const char* aPath) {
+    for (uint32_t i = 0; i < uint32_t(GetSize()); ++i) {
+      ResourceItem* item = ResourceAt(i);
+
+      char buf[255];
+      PR_snprintf(buf, sizeof(buf), "%s/%08u.bin", aPath, i);
+      FILE* fp = fopen(buf, "wb");
+      if (!fp) {
+        return;
+      }
+      fwrite(item->mData.Elements(), item->mData.Length(), 1, fp);
+      fclose(fp);
+    }
+  }
+#endif
+
 private:
   ResourceItem* ResourceAt(uint32_t aIndex) const {
     return static_cast<ResourceItem*>(ObjectAt(aIndex));
   }
 
   // Returns the index of the resource that contains the given
   // logical offset. aResourceOffset will contain the offset into
   // the resource at the given index returned if it is not null.  If
@@ -168,11 +185,10 @@ private:
 
   // Logical length of the resource.
   uint64_t mLogicalLength;
 
   // Logical offset into the resource of the first element in the queue.
   uint64_t mOffset;
 };
 
-
 } // namespace mozilla
 #endif /* MOZILLA_RESOURCEQUEUE_H_ */

--- a/content/media/mediasource/SourceBuffer.cpp
+++ b/content/media/mediasource/SourceBuffer.cpp
@@ -1,8 +1,9 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * 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/. */
 
 #include "SourceBuffer.h"
 
 #include "AsyncEventRunner.h"
@@ -682,16 +683,26 @@ SourceBuffer::Evict(double aStart, doubl
   double evictTime = aEnd;
   const double safety_threshold = 5;
   if (currentTime + safety_threshold >= evictTime) {
     evictTime -= safety_threshold;
   }
   mTrackBuffer->EvictBefore(evictTime);
 }
 
+#if defined(DEBUG)
+void
+SourceBuffer::Dump(const char* aPath)
+{
+  if (mTrackBuffer) {
+    mTrackBuffer->Dump(aPath);
+  }
+}
+#endif
+
 NS_IMPL_CYCLE_COLLECTION_INHERITED(SourceBuffer, DOMEventTargetHelper,
                                    mMediaSource)
 
 NS_IMPL_ADDREF_INHERITED(SourceBuffer, DOMEventTargetHelper)
 NS_IMPL_RELEASE_INHERITED(SourceBuffer, DOMEventTargetHelper)
 
 NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION_INHERITED(SourceBuffer)
 NS_INTERFACE_MAP_END_INHERITING(DOMEventTargetHelper)

--- a/content/media/mediasource/SourceBuffer.h
+++ b/content/media/mediasource/SourceBuffer.h
@@ -104,16 +104,20 @@ public:
   void Ended();
 
   // Evict data in the source buffer in the given time range.
   void Evict(double aStart, double aEnd);
 
   double GetBufferedStart();
   double GetBufferedEnd();
 
+#if defined(DEBUG)
+  void Dump(const char* aPath);
+#endif
+
 private:
   ~SourceBuffer();
 
   friend class AsyncEventRunner<SourceBuffer>;
   void DispatchSimpleEvent(const char* aName);
   void QueueAsyncSimpleEvent(const char* aName);
 
   // Create a new decoder for mType, and store the result in mDecoder.

--- a/content/media/mediasource/SourceBufferDecoder.cpp
+++ b/content/media/mediasource/SourceBufferDecoder.cpp
@@ -1,8 +1,9 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * 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/. */
 
 #include "SourceBufferDecoder.h"
 #include "prlog.h"
 #include "AbstractMediaDecoder.h"

--- a/content/media/mediasource/SourceBufferList.cpp
+++ b/content/media/mediasource/SourceBufferList.cpp
@@ -162,16 +162,26 @@ SourceBufferList::DispatchSimpleEvent(co
 void
 SourceBufferList::QueueAsyncSimpleEvent(const char* aName)
 {
   MSE_DEBUG("SourceBufferList(%p) Queuing event '%s'", this, aName);
   nsCOMPtr<nsIRunnable> event = new AsyncEventRunner<SourceBufferList>(this, aName);
   NS_DispatchToMainThread(event);
 }
 
+#if defined(DEBUG)
+void
+SourceBufferList::Dump(const char* aPath)
+{
+  for (uint32_t i = 0; i < mSourceBuffers.Length(); ++i) {
+    mSourceBuffers[i]->Dump(aPath);
+  }
+}
+#endif
+
 SourceBufferList::SourceBufferList(MediaSource* aMediaSource)
   : DOMEventTargetHelper(aMediaSource->GetParentObject())
   , mMediaSource(aMediaSource)
 {
   MOZ_ASSERT(aMediaSource);
 }
 
 MediaSource*

--- a/content/media/mediasource/SourceBufferList.h
+++ b/content/media/mediasource/SourceBufferList.h
@@ -74,16 +74,20 @@ public:
   void Ended();
 
   // Evicts data for the given time range from each SourceBuffer in the list.
   void Evict(double aStart, double aEnd);
 
   // Returns the highest end time of any of the Sourcebuffers.
   double GetHighestBufferedEndTime();
 
+#if defined(DEBUG)
+  void Dump(const char* aPath);
+#endif
+
 private:
   ~SourceBufferList();
 
   friend class AsyncEventRunner<SourceBufferList>;
   void DispatchSimpleEvent(const char* aName);
   void QueueAsyncSimpleEvent(const char* aName);
 
   nsRefPtr<MediaSource> mMediaSource;

--- a/content/media/mediasource/SourceBufferResource.h
+++ b/content/media/mediasource/SourceBufferResource.h
@@ -115,16 +115,22 @@ public:
   void Ended();
   // Remove data from resource if it holds more than the threshold
   // number of bytes. Returns true if some data was evicted.
   bool EvictData(uint32_t aThreshold);
 
   // Remove data from resource before the given offset.
   void EvictBefore(uint64_t aOffset);
 
+#if defined(DEBUG)
+  void Dump(const char* aPath) {
+    mInputBuffer.Dump(aPath);
+  }
+#endif
+
 private:
   ~SourceBufferResource();
   nsresult SeekInternal(int64_t aOffset);
 
   const nsCString mType;
 
   // Provides synchronization between SourceBuffers and InputAdapters.
   // Protects all of the member variables below.  Read() will await a

--- a/content/media/mediasource/TrackBuffer.cpp
+++ b/content/media/mediasource/TrackBuffer.cpp
@@ -1,8 +1,9 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * 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/. */
 
 #include "TrackBuffer.h"
 
 #include "MediaSourceDecoder.h"
@@ -344,9 +345,27 @@ TrackBuffer::ResetDecode()
 
 const nsTArray<nsRefPtr<SourceBufferDecoder>>&
 TrackBuffer::Decoders()
 {
   // XXX assert OnDecodeThread
   return mInitializedDecoders;
 }
 
+#if defined(DEBUG)
+void
+TrackBuffer::Dump(const char* aPath)
+{
+  char path[255];
+  PR_snprintf(path, sizeof(path), "%s/trackbuffer-%p", aPath, this);
+  mkdir(path, 0700);
+
+  for (uint32_t i = 0; i < mDecoders.Length(); ++i) {
+    char buf[255];
+    PR_snprintf(buf, sizeof(buf), "%s/reader-%p", path, mDecoders[i]->GetReader());
+    mkdir(buf, 0700);
+
+    mDecoders[i]->GetResource()->Dump(buf);
+  }
+}
+#endif
+
 } // namespace mozilla

--- a/content/media/mediasource/TrackBuffer.h
+++ b/content/media/mediasource/TrackBuffer.h
@@ -77,16 +77,20 @@ public:
   // Call ResetDecode() on each decoder in mDecoders.
   void ResetDecode();
 
   // Returns a reference to mInitializedDecoders, used by MediaSourceReader
   // to select decoders.
   // TODO: Refactor to a cleaner interface between TrackBuffer and MediaSourceReader.
   const nsTArray<nsRefPtr<SourceBufferDecoder>>& Decoders();
 
+#if defined(DEBUG)
+  void Dump(const char* aPath);
+#endif
+
 private:
   ~TrackBuffer();
 
   // Queue execution of InitializeDecoder on mTaskQueue.
   bool QueueInitializeDecoder(nsRefPtr<SourceBufferDecoder> aDecoder);
 
   // Runs decoder initialization including calling ReadMetadata.  Runs as an
   // event on the decode thread pool.