b=856850 use PodMove for potentially overlapping buffers r=roc

--HG--
extra : transplant_source : %A2%F8%85%0C%08%86%CE%E2%7F%A7X%9F%F1%B7%0E%3F%16%1E%BF%3F

content/media/webaudio/AudioBuffer.cpp

@@ -131,7 +131,7 @@ AudioBuffer::CopyFromChannel(const Float32Array& aDestination, uint32_t aChannel
   const float* sourceData = mSharedChannels ?
     mSharedChannels->GetData(aChannelNumber) :
     JS_GetFloat32ArrayData(mJSChannels[aChannelNumber]);
-  PodCopy(aDestination.Data(), sourceData + aStartInChannel, length);
+  PodMove(aDestination.Data(), sourceData + aStartInChannel, length);
 }
 
 void
@@ -159,7 +159,7 @@ AudioBuffer::CopyToChannel(JSContext* aJSContext, const Float32Array& aSource,
     return;
   }
 
-  PodCopy(JS_GetFloat32ArrayData(mJSChannels[aChannelNumber]) + aStartInChannel,
+  PodMove(JS_GetFloat32ArrayData(mJSChannels[aChannelNumber]) + aStartInChannel,
           aSource.Data(), length);
 }