Revert "Eliminate unreachable code."

This reverts commit df07d66c.

Reason for revert: Causing compile failures on linux-chromeos-chrome
https://ci.chromium.org/p/chrome/builders/ci/linux-chromeos-chrome/4233

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=pkasting@chromium.org,rockot@google.com,kmackay@chromium.org

Change-Id: I6f2787f775d211322b8c200410a07f48f0782f9d
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 346399
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2116165Reviewed-by: calamity <calamity@chromium.org>
Commit-Queue: calamity <calamity@chromium.org>
Cr-Commit-Position: refs/heads/master@{#752721}

chromecast/media/cma/backend/volume_control.cc

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