Re-enable always-on hotwording for m42 on supported hardware.

Revert "Remove hardware check that enables always-on hotwording."

This reverts commit e014345e.

Review URL: https://codereview.chromium.org/838753004

Cr-Commit-Position: refs/heads/master@{#313214}

chrome/browser/search/hotword_service_factory.cc

@@ -47,9 +47,6 @@ bool HotwordServiceFactory::IsHotwordAllowed(BrowserContext* context) {
 
 // static
 bool HotwordServiceFactory::IsHotwordHardwareAvailable() {
-// Temporarily disabling hotword hardware check for M41. Will be
-// re-enabled for M42.
-#if 0
 #if defined(OS_CHROMEOS)
   if (chromeos::CrasAudioHandler::IsInitialized()) {
     chromeos::AudioDeviceList devices;
@@ -62,7 +59,6 @@ bool HotwordServiceFactory::IsHotwordHardwareAvailable() {
     }
   }
 #endif
-#endif  // 0
   base::CommandLine* command_line = base::CommandLine::ForCurrentProcess();
   return command_line->HasSwitch(switches::kEnableExperimentalHotwordHardware);
 }