clang/win: Enable -Wswitch.

chrome/browser/metrics/chrome_metrics_service_client.cc

Index: chrome/browser/metrics/chrome_metrics_service_client.cc
diff --git a/chrome/browser/metrics/chrome_metrics_service_client.cc b/chrome/browser/metrics/chrome_metrics_service_client.cc
index 3f7a88858d3179153c1d7fed1d3bdb09e27a05ba..c8ade380c10709743e00c1bab3a148b944b37f5d 100644
--- a/chrome/browser/metrics/chrome_metrics_service_client.cc
+++ b/chrome/browser/metrics/chrome_metrics_service_client.cc
@@ -391,6 +391,12 @@ void ChromeMetricsServiceClient::Initialize() {
     case version_info::Channel::DEV:
       report_exit_funnels = true;
       break;
+    case version_info::Channel::UNKNOWN:
+    case version_info::Channel::BETA:
+    case version_info::Channel::STABLE:
+      // report_exit_funnels was initialized to the right value above.
+      DCHECK(!report_exit_funnels);
+      break;
   }
 
   metrics_service_->RegisterMetricsProvider(