aaudio: add thread safety annotation

Also improve naming to clarify lock requirements.

And call some locked methods that were not called before.
Although they were protected with a different lock so
it should have no effect.

Bug: 171296283
Test: adb logcat *:F
Test: In another window:
Test: atest AAudioTestCases
Change-Id: I6e863cbdea9250188e3f4b8f8654ef71c8951e74
diff --git a/media/libaaudio/src/legacy/AudioStreamTrack.h b/media/libaaudio/src/legacy/AudioStreamTrack.h
index 654ea9b..f604871 100644
--- a/media/libaaudio/src/legacy/AudioStreamTrack.h
+++ b/media/libaaudio/src/legacy/AudioStreamTrack.h
@@ -44,11 +44,13 @@
     aaudio_result_t release_l() override;
     void close_l() override;
 
-    aaudio_result_t requestStart_l() override;
-    aaudio_result_t requestPause_l() override;
-    aaudio_result_t requestFlush_l() override;
-    aaudio_result_t requestStop_l() override;
+protected:
+    aaudio_result_t requestStart_l() REQUIRES(mStreamLock)  override;
+    aaudio_result_t requestPause_l() REQUIRES(mStreamLock) override;
+    aaudio_result_t requestFlush_l() REQUIRES(mStreamLock) override;
+    aaudio_result_t requestStop_l() REQUIRES(mStreamLock) override;
 
+public:
     bool isFlushSupported() const override {
         // Only implement FLUSH for OUTPUT streams.
         return true;