diff --git a/content/media/webaudio/AudioBuffer.cpp b/content/media/webaudio/AudioBuffer.cpp
index edc8f675c69..bc4377ab141 100644
--- a/content/media/webaudio/AudioBuffer.cpp
+++ b/content/media/webaudio/AudioBuffer.cpp
@@ -165,8 +165,7 @@ StealJSArrayDataIntoThreadSharedFloatArrayBufferList(JSContext* aJSContext,
 }
 
 ThreadSharedFloatArrayBufferList*
-AudioBuffer::GetThreadSharedChannelsForRate(JSContext* aJSContext, uint32_t* aRate,
-                                            uint32_t* aLength)
+AudioBuffer::GetThreadSharedChannelsForRate(JSContext* aJSContext)
 {
   if (!mSharedChannels) {
     // Steal JS data
@@ -174,8 +173,6 @@ AudioBuffer::GetThreadSharedChannelsForRate(JSContext* aJSContext, uint32_t* aRa
       StealJSArrayDataIntoThreadSharedFloatArrayBufferList(aJSContext, mJSChannels);
   }
 
-  *aLength = mLength;
-  *aRate = mSampleRate;
   return mSharedChannels;
 }
 
diff --git a/content/media/webaudio/AudioBuffer.h b/content/media/webaudio/AudioBuffer.h
index 6d2056c9f56..f9ff7d2d25a 100644
--- a/content/media/webaudio/AudioBuffer.h
+++ b/content/media/webaudio/AudioBuffer.h
@@ -89,12 +89,9 @@ public:
   }
 
   /**
-   * Returns a ThreadSharedFloatArrayBufferList containing the sample data
-   * at aRate. Sets *aLength to the number of samples per channel.
+   * Returns a ThreadSharedFloatArrayBufferList containing the sample data.
    */
-  ThreadSharedFloatArrayBufferList* GetThreadSharedChannelsForRate(JSContext* aContext,
-                                                                   uint32_t* aRate,
-                                                                   uint32_t* aLength);
+  ThreadSharedFloatArrayBufferList* GetThreadSharedChannelsForRate(JSContext* aContext);
 
   // aContents should either come from JS_AllocateArrayBufferContents or
   // JS_StealArrayBufferContents.
diff --git a/content/media/webaudio/AudioBufferSourceNode.cpp b/content/media/webaudio/AudioBufferSourceNode.cpp
index 334fe945593..9f8e04a6e96 100644
--- a/content/media/webaudio/AudioBufferSourceNode.cpp
+++ b/content/media/webaudio/AudioBufferSourceNode.cpp
@@ -457,10 +457,10 @@ AudioBufferSourceNode::Start(JSContext* aCx, double aWhen, double aOffset,
     return;
   }
 
-  uint32_t rate;
-  uint32_t lengthSamples;
+  float rate = mBuffer->SampleRate();
+  int32_t lengthSamples = mBuffer->Length();
   nsRefPtr<ThreadSharedFloatArrayBufferList> data =
-    mBuffer->GetThreadSharedChannelsForRate(aCx, &rate, &lengthSamples);
+    mBuffer->GetThreadSharedChannelsForRate(aCx);
   double length = double(lengthSamples) / rate;
   double offset = std::max(0.0, aOffset);
   double endOffset = aDuration.WasPassed() ?
diff --git a/content/media/webaudio/ScriptProcessorNode.cpp b/content/media/webaudio/ScriptProcessorNode.cpp
index 0eff188de5c..61b3f6cf4eb 100644
--- a/content/media/webaudio/ScriptProcessorNode.cpp
+++ b/content/media/webaudio/ScriptProcessorNode.cpp
@@ -13,7 +13,6 @@
 #include "AudioProcessingEvent.h"
 #include "WebAudioUtils.h"
 #include "mozilla/Mutex.h"
-#include "mozilla/unused.h"
 #include "mozilla/PodOperations.h"
 #include <deque>
 
@@ -304,10 +303,7 @@ private:
           // Steal the output buffers
           nsRefPtr<ThreadSharedFloatArrayBufferList> output;
           if (event->HasOutputBuffer()) {
-            uint32_t rate, length;
-            output = event->OutputBuffer()->GetThreadSharedChannelsForRate(cx, &rate, &length);
-            unused << rate;
-            unused << length;
+            output = event->OutputBuffer()->GetThreadSharedChannelsForRate(cx);
           }
 
           // Append it to our output buffer queue