Pass switch --use-cras to new process

We need to pass switch --use-cras to the audio service so that chrome
will be able to use CRAS on linux.

Bug: 151905045
Change-Id: I7c8acf0f3c976ba40bf492a85a53c56a3254fcfe
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2332057Reviewed-by: Dale Curtis <dalecurtis@chromium.org>
Reviewed-by: Bo <boliu@chromium.org>
Reviewed-by: Alex Moshchuk <alexmos@chromium.org>
Commit-Queue: Yu-Hsuan Hsu <yuhsuan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#797769}

content/browser/BUILD.gn

@@ -2731,6 +2731,10 @@ source_set("browser") {
     deps += [ "//ui/ozone" ]
   }
 
+  if (use_cras) {
+    defines += [ "USE_CRAS" ]
+  }
+
   if (enable_ipc_fuzzer) {
     configs += [ "//tools/ipc_fuzzer:ipc_fuzzer_config" ]
   }

content/browser/utility_process_host.cc

@@ -274,6 +274,9 @@ bool UtilityProcessHost::StartProcess() {
       switches::kAlsaInputDevice,
       switches::kAlsaOutputDevice,
 #endif
+#if defined(USE_CRAS)
+      switches::kUseCras,
+#endif
 #if defined(OS_WIN)
       switches::kDisableHighResTimer,
       switches::kEnableExclusiveAudio,