Code clean for audioflinger

Cleaning compile warnings:
1. For "variable 'XX' set but not used":
   Remove the variables which are obviously not used;
   Add "[[maybe_unused]]" to variable declaration of the ones
       which are potentially used.
2. For "unused parameter 'XX'":
   Add "[[maybe_unused]]" to the unused function parameters.

Test: mmm frameworks/av/services/audioflinger, presubmit check.

Change-Id: I6bd6fa9a57de93f5387e1ad76342f0a0b0ac28ed
Signed-off-by: Jing Mike <jingyangliu@eswincomputing.com>
diff --git a/services/audioflinger/AudioFlinger.cpp b/services/audioflinger/AudioFlinger.cpp
index c05aac1..ba7c6b6 100644
--- a/services/audioflinger/AudioFlinger.cpp
+++ b/services/audioflinger/AudioFlinger.cpp
@@ -4585,12 +4585,9 @@
 // ----------------------------------------------------------------------------
 
 status_t AudioFlinger::onTransactWrapper(TransactionCode code,
-                                         const Parcel& data,
-                                         uint32_t flags,
+                                         [[maybe_unused]] const Parcel& data,
+                                         [[maybe_unused]] uint32_t flags,
                                          const std::function<status_t()>& delegate) {
-    (void) data;
-    (void) flags;
-
     // make sure transactions reserved to AudioPolicyManager do not come from other processes
     switch (code) {
         case TransactionCode::SET_STREAM_VOLUME:
diff --git a/services/audioflinger/FastMixer.cpp b/services/audioflinger/FastMixer.cpp
index 26bd92d..61dd3f2 100644
--- a/services/audioflinger/FastMixer.cpp
+++ b/services/audioflinger/FastMixer.cpp
@@ -79,8 +79,6 @@
     mMasterMono(false),
     mThreadIoHandle(parentIoHandle)
 {
-    (void)mThreadIoHandle; // prevent unused warning, see C++17 [[maybe_unused]]
-
     // FIXME pass sInitial as parameter to base class constructor, and make it static local
     mPrevious = &sInitial;
     mCurrent = &sInitial;
diff --git a/services/audioflinger/FastMixer.h b/services/audioflinger/FastMixer.h
index 97ab635..d71519f 100644
--- a/services/audioflinger/FastMixer.h
+++ b/services/audioflinger/FastMixer.h
@@ -107,7 +107,8 @@
     std::atomic<float> mMasterBalance{};
     std::atomic_int_fast64_t mBoottimeOffset;
 
-    const audio_io_handle_t mThreadIoHandle; // parent thread id for debugging purposes
+    // parent thread id for debugging purposes
+    [[maybe_unused]] const audio_io_handle_t mThreadIoHandle;
 #ifdef TEE_SINK
     NBAIO_Tee       mTee;
 #endif
diff --git a/services/audioflinger/Threads.cpp b/services/audioflinger/Threads.cpp
index b72348a..37b8fe8 100644
--- a/services/audioflinger/Threads.cpp
+++ b/services/audioflinger/Threads.cpp
@@ -3293,7 +3293,7 @@
 }
 
 void AudioFlinger::PlaybackThread::threadLoop_removeTracks(
-        const Vector< sp<Track> >& tracksToRemove)
+        [[maybe_unused]] const Vector< sp<Track> >& tracksToRemove)
 {
     // Miscellaneous track cleanup when removed from the active list,
     // called without Thread lock but synchronized with threadLoop processing.
@@ -3304,8 +3304,6 @@
             addBatteryData(IMediaPlayerService::kBatteryDataAudioFlingerStop);
         }
     }
-#else
-    (void)tracksToRemove; // suppress unused warning
 #endif
 }
 
@@ -5829,7 +5827,7 @@
     }
 
     // Push the new FastMixer state if necessary
-    bool pauseAudioWatchdog = false;
+    [[maybe_unused]] bool pauseAudioWatchdog = false;
     if (didModify) {
         state->mFastTracksGen++;
         // if the fast mixer was active, but now there are no fast tracks, then put it in cold idle
@@ -7570,7 +7568,7 @@
     size_t numCounterOffers = 0;
     const NBAIO_Format offers[1] = {Format_from_SR_C(mSampleRate, mChannelCount, mFormat)};
 #if !LOG_NDEBUG
-    ssize_t index =
+    [[maybe_unused]] ssize_t index =
 #else
     (void)
 #endif
@@ -7621,7 +7619,7 @@
         Pipe *pipe = new Pipe(pipeFramesP2, format, pipeBuffer);
         const NBAIO_Format offers[1] = {format};
         size_t numCounterOffers = 0;
-        ssize_t index = pipe->negotiate(offers, 1, NULL, numCounterOffers);
+        [[maybe_unused]] ssize_t index = pipe->negotiate(offers, 1, NULL, numCounterOffers);
         ALOG_ASSERT(index == 0);
         mPipeSink = pipe;
         PipeReader *pipeReader = new PipeReader(*pipe);
@@ -9077,7 +9075,8 @@
     audio_format_t reqFormat = mFormat;
     uint32_t samplingRate = mSampleRate;
     // TODO this may change if we want to support capture from HDMI PCM multi channel (e.g on TVs).
-    audio_channel_mask_t channelMask = audio_channel_in_mask_from_count(mChannelCount);
+    [[maybe_unused]] audio_channel_mask_t channelMask =
+                                audio_channel_in_mask_from_count(mChannelCount);
 
     AudioParameter param = AudioParameter(keyValuePair);
     int value;