Reland "Eliminate unreachable code."

This is a reland of df07d66c

This was reverted due to a sheriffing misfire.

Original change's description:
> Eliminate unreachable code.
>
> This converts runtime checking of BUILDFLAG output to compile-time
> checking.  It also converts NOTREACHED to DLOG(ERROR).
>
> Bug: 346399
> Change-Id: I85dc2e655a1badccb117bb566f8812c6962416b6
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2114400
> Commit-Queue: Peter Kasting <pkasting@chromium.org>
> Reviewed-by: Kenneth MacKay <kmackay@chromium.org>
> Auto-Submit: Peter Kasting <pkasting@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#752603}

TBR=kmackay@chromium.org

Bug: 346399
Change-Id: I688c6405360636b892dfd8d2c86bb2ccd55fdb60
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2115866Reviewed-by: calamity <calamity@chromium.org>
Commit-Queue: calamity <calamity@chromium.org>
Cr-Commit-Position: refs/heads/master@{#752727}

chromecast/media/cma/backend/volume_control.cc

@@ -154,7 +154,7 @@ class VolumeControlInternal : public SystemVolumeControl::Delegate {
                  AudioContentType type,
                  float level) {
     if (type == AudioContentType::kOther) {
-      NOTREACHED() << "Can't set volume for content type kOther";
+      DLOG(ERROR) << "Can't set volume for content type kOther";
       return;
     }
 
@@ -167,20 +167,19 @@ class VolumeControlInternal : public SystemVolumeControl::Delegate {
 
   void SetVolumeMultiplier(AudioContentType type, float multiplier) {
     if (type == AudioContentType::kOther) {
-      NOTREACHED() << "Can't set volume multiplier for content type kOther";
-      return;
-    }
-
-    if (BUILDFLAG(SYSTEM_OWNS_VOLUME)) {
-      LOG(INFO) << "Ignore global volume multiplier since volume is externally "
-                << "controlled";
+      DLOG(ERROR) << "Can't set volume multiplier for content type kOther";
       return;
     }
 
+#if BUILDFLAG(SYSTEM_OWNS_VOLUME)
+    LOG(INFO) << "Ignore global volume multiplier since volume is externally "
+              << "controlled";
+#else
     thread_.task_runner()->PostTask(
         FROM_HERE,
         base::BindOnce(&VolumeControlInternal::SetVolumeMultiplierOnThread,
                        base::Unretained(this), type, multiplier));
+#endif
   }
 
   bool IsMuted(AudioContentType type) {
@@ -190,7 +189,7 @@ class VolumeControlInternal : public SystemVolumeControl::Delegate {
 
   void SetMuted(VolumeChangeSource source, AudioContentType type, bool muted) {
     if (type == AudioContentType::kOther) {
-      NOTREACHED() << "Can't set mute state for content type kOther";
+      DLOG(ERROR) << "Can't set mute state for content type kOther";
       return;
     }
 
@@ -202,7 +201,7 @@ class VolumeControlInternal : public SystemVolumeControl::Delegate {
 
   void SetOutputLimit(AudioContentType type, float limit) {
     if (type == AudioContentType::kOther) {
-      NOTREACHED() << "Can't set output limit for content type kOther";
+      DLOG(ERROR) << "Can't set output limit for content type kOther";
       return;
     }
 
@@ -234,28 +233,27 @@ class VolumeControlInternal : public SystemVolumeControl::Delegate {
       volume_multipliers_[type] = 1.0f;
 
 #if BUILDFLAG(SYSTEM_OWNS_VOLUME)
-      // If ALSA owns volume, our internal mixer should not apply any scaling
+      // ALSA owns volume; our internal mixer should not apply any scaling
       // multiplier.
       mixer_->SetVolume(type, 1.0f);
-#else   // BUILDFLAG(SYSTEM_OWNS_VOLUME)
+#else
       mixer_->SetVolume(type, DbFsToScale(dbfs));
-#endif  // BUILDFLAG(SYSTEM_OWNS_VOLUME)
+#endif
 
       // Note that mute state is not persisted across reboots.
       muted_[type] = false;
     }
 
 #if BUILDFLAG(SYSTEM_OWNS_VOLUME)
-    // If ALSA owns the volume, then read the current volume and mute state
-    // from the ALSA mixer element(s).
+    // Read the current volume and mute state from the ALSA mixer element(s).
     volumes_[AudioContentType::kMedia] = system_volume_control_->GetVolume();
     muted_[AudioContentType::kMedia] = system_volume_control_->IsMuted();
-#else   // BUILDFLAG(SYSTEM_OWNS_VOLUME)
-    // Otherwise, make sure the ALSA mixer element correctly reflects the
-    // current volume state.
+#else
+    // Make sure the ALSA mixer element correctly reflects the current volume
+    // state.
     system_volume_control_->SetVolume(volumes_[AudioContentType::kMedia]);
     system_volume_control_->SetMuted(false);
-#endif  // BUILDFLAG(SYSTEM_OWNS_VOLUME)
+#endif
 
     volumes_[AudioContentType::kOther] = 1.0;
     muted_[AudioContentType::kOther] = false;
@@ -268,7 +266,7 @@ class VolumeControlInternal : public SystemVolumeControl::Delegate {
                          float level,
                          bool from_system) {
     DCHECK(thread_.task_runner()->BelongsToCurrentThread());
-    DCHECK(type != AudioContentType::kOther);
+    DCHECK_NE(AudioContentType::kOther, type);
     DCHECK(!from_system || type == AudioContentType::kMedia);
     DCHECK(volume_multipliers_.find(type) != volume_multipliers_.end());
 
@@ -285,9 +283,9 @@ class VolumeControlInternal : public SystemVolumeControl::Delegate {
     }
 
     float dbfs = VolumeControl::VolumeToDbFS(level);
-    if (!BUILDFLAG(SYSTEM_OWNS_VOLUME)) {
-      mixer_->SetVolume(type, DbFsToScale(dbfs) * volume_multipliers_[type]);
-    }
+#if !BUILDFLAG(SYSTEM_OWNS_VOLUME)
+    mixer_->SetVolume(type, DbFsToScale(dbfs) * volume_multipliers_[type]);
+#endif
 
     if (!from_system && type == AudioContentType::kMedia) {
       system_volume_control_->SetVolume(level);
@@ -306,13 +304,15 @@ class VolumeControlInternal : public SystemVolumeControl::Delegate {
 
   void SetVolumeMultiplierOnThread(AudioContentType type, float multiplier) {
     DCHECK(thread_.task_runner()->BelongsToCurrentThread());
-    DCHECK(type != AudioContentType::kOther);
-    DCHECK(!BUILDFLAG(SYSTEM_OWNS_VOLUME));
-
+    DCHECK_NE(AudioContentType::kOther, type);
+#if BUILDFLAG(SYSTEM_OWNS_VOLUME)
+    NOTREACHED();
+#else
     volume_multipliers_[type] = multiplier;
     float scale =
         DbFsToScale(VolumeControl::VolumeToDbFS(volumes_[type])) * multiplier;
     mixer_->SetVolume(type, scale);
+#endif
   }
 
   void SetMutedOnThread(VolumeChangeSource source,
@@ -320,7 +320,7 @@ class VolumeControlInternal : public SystemVolumeControl::Delegate {
                         bool muted,
                         bool from_system) {
     DCHECK(thread_.task_runner()->BelongsToCurrentThread());
-    DCHECK(type != AudioContentType::kOther);
+    DCHECK_NE(AudioContentType::kOther, type);
 
     {
       base::AutoLock lock(volume_lock_);
@@ -330,9 +330,9 @@ class VolumeControlInternal : public SystemVolumeControl::Delegate {
       muted_[type] = muted;
     }
 
-    if (!BUILDFLAG(SYSTEM_OWNS_VOLUME)) {
-      mixer_->SetMuted(type, muted);
-    }
+#if !BUILDFLAG(SYSTEM_OWNS_VOLUME)
+    mixer_->SetMuted(type, muted);
+#endif
 
     if (!from_system && type == AudioContentType::kMedia) {
       system_volume_control_->SetMuted(muted);
@@ -348,13 +348,11 @@ class VolumeControlInternal : public SystemVolumeControl::Delegate {
 
   void SetOutputLimitOnThread(AudioContentType type, float limit) {
     if (type == AudioContentType::kOther) {
-      NOTREACHED() << "Can't set output limit for content type kOther";
+      DLOG(ERROR) << "Can't set output limit for content type kOther";
       return;
     }
 
-    if (BUILDFLAG(SYSTEM_OWNS_VOLUME)) {
-      return;
-    }
+#if !BUILDFLAG(SYSTEM_OWNS_VOLUME)
     limit = base::ClampToRange(limit, 0.0f, 1.0f);
     mixer_->SetVolumeLimit(type,
                            DbFsToScale(VolumeControl::VolumeToDbFS(limit)));
@@ -362,6 +360,7 @@ class VolumeControlInternal : public SystemVolumeControl::Delegate {
     if (type == AudioContentType::kMedia) {
       system_volume_control_->SetLimit(limit);
     }
+#endif
   }
 
   void SetPowerSaveModeOnThread(bool power_save_on) {