bug 976927 use nsAutoTArray operator= from nsTArray r=froydnj

--HG--
extra : rebase_source : 59226888a19e525f4925eabdd93d08bfa7db13a9

dom/media/webaudio/DelayBuffer.cpp

@@ -247,9 +247,7 @@ DelayBuffer::UpdateUpmixChannels(int aNewReadChunk, uint32_t aChannelCount,
                    "Smoothing is making feedback delay too small.");
 
   mLastReadChunk = aNewReadChunk;
-  // Missing assignment operator is bug 976927
-  mUpmixChannels.ReplaceElementsAt(0, mUpmixChannels.Length(),
-                                   mChunks[aNewReadChunk].mChannelData);
+  mUpmixChannels = mChunks[aNewReadChunk].mChannelData;
   MOZ_ASSERT(mUpmixChannels.Length() <= aChannelCount);
   if (mUpmixChannels.Length() < aChannelCount) {
     if (aChannelInterpretation == ChannelInterpretation::Speakers) {