aaudio: use unique_ptr for mixer buffer

Bug: 151650670
Test: atest CtsNativeMediaAAudioTestCases
Test: OboeTester "TEST OUTPUT"
Test: disable EXCLUSIVE mode so we use the shared mixer
Change-Id: Ie8bcca265cd3ee124e455116a366d1056f3ee4cb
diff --git a/services/oboeservice/AAudioMixer.h b/services/oboeservice/AAudioMixer.h
index d5abc5b..dd466ac 100644
--- a/services/oboeservice/AAudioMixer.h
+++ b/services/oboeservice/AAudioMixer.h
@@ -25,7 +25,6 @@
 class AAudioMixer {
 public:
     AAudioMixer() {}
-    ~AAudioMixer();
 
     void allocate(int32_t samplesPerFrame, int32_t framesPerBurst);
 
@@ -47,7 +46,7 @@
 private:
     void mixPart(float *destination, float *source, int32_t numFrames);
 
-    float   *mOutputBuffer = nullptr;
+    std::unique_ptr<float[]> mOutputBuffer;
     int32_t  mSamplesPerFrame = 0;
     int32_t  mFramesPerBurst = 0;
     int32_t  mBufferSizeInBytes = 0;