Use audio_io_handle_t consistently instead of int

Other:
 - add a comment to nextUniqueId
 - made ThreadBase::mId const, since it is only assigned in constructor.

Change-Id: I4e8b7bec4e45badcde6274d574b8a9aabd046837
diff --git a/services/audioflinger/AudioPolicyService.cpp b/services/audioflinger/AudioPolicyService.cpp
index 755f51f..10efd85 100644
--- a/services/audioflinger/AudioPolicyService.cpp
+++ b/services/audioflinger/AudioPolicyService.cpp
@@ -819,7 +819,7 @@
 
 status_t AudioPolicyService::AudioCommandThread::volumeCommand(audio_stream_type_t stream,
                                                                float volume,
-                                                               int output,
+                                                               audio_io_handle_t output,
                                                                int delayMs)
 {
     status_t status = NO_ERROR;
@@ -849,7 +849,7 @@
     return status;
 }
 
-status_t AudioPolicyService::AudioCommandThread::parametersCommand(int ioHandle,
+status_t AudioPolicyService::AudioCommandThread::parametersCommand(audio_io_handle_t ioHandle,
                                                                    const char *keyValuePairs,
                                                                    int delayMs)
 {
@@ -1019,7 +1019,7 @@
                                        const char *keyValuePairs,
                                        int delayMs)
 {
-    mAudioCommandThread->parametersCommand((int)ioHandle, keyValuePairs,
+    mAudioCommandThread->parametersCommand(ioHandle, keyValuePairs,
                                            delayMs);
 }
 
@@ -1029,7 +1029,7 @@
                                         int delayMs)
 {
     return (int)mAudioCommandThread->volumeCommand(stream, volume,
-                                                   (int)output, delayMs);
+                                                   output, delayMs);
 }
 
 int AudioPolicyService::startTone(audio_policy_tone_t tone,
@@ -1458,7 +1458,7 @@
     if (af == 0)
         return PERMISSION_DENIED;
 
-    return af->moveEffects(session, (int)src_output, (int)dst_output);
+    return af->moveEffects(session, src_output, dst_output);
 }
 
 static char * aps_get_parameters(void *service, audio_io_handle_t io_handle,