Reland "Enable -Wunreachable-code in Fuchsia builds."

This is a reland of ec7d2855, with fixes
to //chromecast to fix some unreachable code there.

Original change's description:
> Enable -Wunreachable-code in Fuchsia builds.
>
> Depends on https://chromium-review.googlesource.com/c/angle/angle/+/2112281
>
> Bug: 346399
> Change-Id: I6bf27dc15303c207be0ae85dd3256af217db005b
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2111833
> Reviewed-by: Sergey Ulanov <sergeyu@chromium.org>
> Commit-Queue: Nico Weber <thakis@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#752299}

TBR: spang, thakis, kmarshall, sergeyu
Cq-Include-Trybots: luci.chromium.try:fuchsia-arm64-cast;luci.chromium.try:fuchsia-x64-cast
Bug: 346399, 1063669
Change-Id: I87ec7863c1e34e9dbdbde929d9863561c3f5f235
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2113971Reviewed-by: Wez <wez@chromium.org>
Commit-Queue: Wez <wez@chromium.org>
Auto-Submit: Wez <wez@chromium.org>
Cr-Commit-Position: refs/heads/master@{#752337}

build/config/compiler/BUILD.gn

@@ -1591,7 +1591,8 @@ config("chromium_code") {
 
     # TODO(thakis): Enable this more often, https://crbug.com/346399
     # use_libfuzzer: https://crbug.com/1063180
-    if (!is_nacl && target_os == "linux" && !use_libfuzzer) {
+    if (!is_nacl && !use_libfuzzer &&
+        (target_os == "fuchsia" || target_os == "linux")) {
       cflags += [ "-Wunreachable-code" ]
     }
 

chromecast/media/cma/backend/volume_control.cc

@@ -232,29 +232,30 @@ class VolumeControlInternal : public SystemVolumeControl::Delegate {
       CHECK(stored_values_.GetDouble(ContentTypeToDbFSKey(type), &dbfs));
       volumes_[type] = VolumeControl::DbFSToVolume(dbfs);
       volume_multipliers_[type] = 1.0f;
-      if (BUILDFLAG(SYSTEM_OWNS_VOLUME)) {
-        // If ALSA owns volume, our internal mixer should not apply any scaling
-        // multiplier.
-        mixer_->SetVolume(type, 1.0f);
-      } else {
-        mixer_->SetVolume(type, DbFsToScale(dbfs));
-      }
+
+#if BUILDFLAG(SYSTEM_OWNS_VOLUME)
+      // If ALSA owns volume, our internal mixer should not apply any scaling
+      // multiplier.
+      mixer_->SetVolume(type, 1.0f);
+#else   // BUILDFLAG(SYSTEM_OWNS_VOLUME)
+      mixer_->SetVolume(type, DbFsToScale(dbfs));
+#endif  // BUILDFLAG(SYSTEM_OWNS_VOLUME)
 
       // 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).
-      volumes_[AudioContentType::kMedia] = system_volume_control_->GetVolume();
-      muted_[AudioContentType::kMedia] = system_volume_control_->IsMuted();
-    } else {
-      // 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);
-    }
+#if BUILDFLAG(SYSTEM_OWNS_VOLUME)
+    // 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   // 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  // BUILDFLAG(SYSTEM_OWNS_VOLUME)
 
     volumes_[AudioContentType::kOther] = 1.0;
     muted_[AudioContentType::kOther] = false;

fuchsia/runners/common/web_content_runner.cc

@@ -74,8 +74,9 @@ void WebContentRunner::StartComponent(
       this,
       std::make_unique<base::fuchsia::StartupContext>(std::move(startup_info)),
       std::move(controller_request));
-  if (BUILDFLAG(WEB_RUNNER_REMOTE_DEBUGGING_PORT) != 0)
-    component->EnableRemoteDebugging();
+#if BUILDFLAG(WEB_RUNNER_REMOTE_DEBUGGING_PORT) != 0
+  component->EnableRemoteDebugging();
+#endif
   component->StartComponent();
   component->LoadUrl(url, std::vector<fuchsia::net::http::Header>());
   RegisterComponent(std::move(component));

fuchsia/runners/web/main.cc

@@ -42,10 +42,10 @@ int main(int argc, char** argv) {
       base::FilePath(base::fuchsia::kPersistedDataDirectoryPath)));
   CHECK(create_context_params.data_directory());
 
-  if (BUILDFLAG(WEB_RUNNER_REMOTE_DEBUGGING_PORT) != 0) {
-    create_context_params.set_remote_debugging_port(
-        BUILDFLAG(WEB_RUNNER_REMOTE_DEBUGGING_PORT));
-  }
+#if BUILDFLAG(WEB_RUNNER_REMOTE_DEBUGGING_PORT) != 0
+  create_context_params.set_remote_debugging_port(
+      BUILDFLAG(WEB_RUNNER_REMOTE_DEBUGGING_PORT));
+#endif
 
   WebContentRunner runner(
       std::move(create_context_params),

third_party/blink/renderer/platform/scheduler/common/thread_cpu_throttler.cc

@@ -167,15 +167,16 @@ void ThreadCPUThrottler::ThrottlingThread::Throttle() {
 }
 
 void ThreadCPUThrottler::ThrottlingThread::Start() {
-#ifdef USE_SIGNALS
+#if defined(USE_SIGNALS) || defined(OS_WIN)
+#if defined(USE_SIGNALS)
   InstallSignalHandler();
-#elif !defined(OS_WIN)
-  LOG(ERROR) << "CPU throttling is not supported.";
-  return;
 #endif
   if (!base::PlatformThread::Create(0, this, &throttling_thread_handle_)) {
     LOG(ERROR) << "Failed to create throttling thread.";
   }
+#else
+  LOG(ERROR) << "CPU throttling is not supported.";
+#endif
 }
 
 void ThreadCPUThrottler::ThrottlingThread::Sleep(base::TimeDelta duration) {