Backed out changeset d271b9e473fd (bug 1122788) for being a possible cause of test_fileapi.html bustage CLOSED TREE

--HG--
extra : commitid : JtZfexvrBDK

xpcom/io/nsMultiplexInputStream.cpp

@@ -141,10 +141,25 @@ nsMultiplexInputStream::GetCount(uint32_t* aCount)
   return NS_OK;
 }
 
+#ifdef DEBUG
+static bool
+SeekableStreamAtBeginning(nsIInputStream* aStream)
+{
+  int64_t streamPos;
+  nsCOMPtr<nsISeekableStream> stream = do_QueryInterface(aStream);
+  if (stream && NS_SUCCEEDED(stream->Tell(&streamPos)) && streamPos != 0) {
+    return false;
+  }
+  return true;
+}
+#endif
+
 NS_IMETHODIMP
 nsMultiplexInputStream::AppendStream(nsIInputStream* aStream)
 {
   MutexAutoLock lock(mLock);
+  NS_ASSERTION(SeekableStreamAtBeginning(aStream),
+               "Appended stream not at beginning.");
   return mStreams.AppendElement(aStream) ? NS_OK : NS_ERROR_OUT_OF_MEMORY;
 }
 
@@ -152,6 +167,8 @@ NS_IMETHODIMP
 nsMultiplexInputStream::InsertStream(nsIInputStream* aStream, uint32_t aIndex)
 {
   MutexAutoLock lock(mLock);
+  NS_ASSERTION(SeekableStreamAtBeginning(aStream),
+               "Inserted stream not at beginning.");
   mStreams.InsertElementAt(aIndex, aStream);
   if (mCurrentStream > aIndex ||
       (mCurrentStream == aIndex && mStartedReadingCurrent)) {