aaudio: fix device switch detection in legacy path

Implement device switch detection on legacy path (AudioTrack and
AudioRecord) based on audio routing callbacks forcing the stream state
to disconnected.

Bug: 33355262
Bug: 62090113
Test: tested with write_sine and input_monitor command line tools.
Change-Id: I9e0421fee233964b1bf318acb640569196a00f13
diff --git a/media/libaudioclient/AudioSystem.cpp b/media/libaudioclient/AudioSystem.cpp
index 5cd2789..9ef1db7 100644
--- a/media/libaudioclient/AudioSystem.cpp
+++ b/media/libaudioclient/AudioSystem.cpp
@@ -19,6 +19,7 @@
 
 #include <utils/Log.h>
 #include <binder/IServiceManager.h>
+#include <binder/ProcessState.h>
 #include <media/AudioSystem.h>
 #include <media/IAudioFlinger.h>
 #include <media/IAudioPolicyService.h>
@@ -68,6 +69,8 @@
             gAudioFlinger = interface_cast<IAudioFlinger>(binder);
             LOG_ALWAYS_FATAL_IF(gAudioFlinger == 0);
             afc = gAudioFlingerClient;
+            // Make sure callbacks can be received by gAudioFlingerClient
+            ProcessState::self()->startThreadPool();
         }
         af = gAudioFlinger;
     }
@@ -711,6 +714,8 @@
             gAudioPolicyService = interface_cast<IAudioPolicyService>(binder);
             LOG_ALWAYS_FATAL_IF(gAudioPolicyService == 0);
             apc = gAudioPolicyServiceClient;
+            // Make sure callbacks can be received by gAudioPolicyServiceClient
+            ProcessState::self()->startThreadPool();
         }
         ap = gAudioPolicyService;
     }