aaudio: add setPerformanceMode()

The performance mode affects the latency and the implementation of the
data path.

MMAP is still disabled for now.

Bug: 37867485
Test: write_sine.cpp
Change-Id: I9bf5d5d13d1047d5ace69bd5ebdce7b6d65c14e7
Signed-off-by: Phil Burk <philburk@google.com>
diff --git a/media/libaaudio/src/client/AudioStreamInternal.h b/media/libaaudio/src/client/AudioStreamInternal.h
index 18a55cf..a43f6c5 100644
--- a/media/libaaudio/src/client/AudioStreamInternal.h
+++ b/media/libaaudio/src/client/AudioStreamInternal.h
@@ -90,6 +90,11 @@
     // Called internally from 'C'
     void *callbackLoop();
 
+
+    bool isMMap() override {
+        return true;
+    }
+
 protected:
 
     aaudio_result_t processCommands();