Fix ArcBridgeBootstrap race issues.

components/arc/arc_bridge_service.cc

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "components/arc/arc_bridge_service.h"
 
 #include <utility>
 
 #include "base/command_line.h"
 #include "base/feature_list.h"
@@ skipping 70 matching lines @@
 
 void ArcBridgeService::SetStopReason(StopReason stop_reason) {
   DCHECK(CalledOnValidThread());
   stop_reason_ = stop_reason;
 }
 
 bool ArcBridgeService::CalledOnValidThread() {
   return thread_checker_.CalledOnValidThread();
 }
 
+std::ostream& operator<<(
+    std::ostream& os, ArcBridgeService::StopReason reason) {
+  switch (reason) {
+#define CASE_IMPL(val) \
+    case ArcBridgeService::StopReason::val: \
+      return os << #val
+
+    CASE_IMPL(SHUTDOWN);
+    CASE_IMPL(GENERIC_BOOT_FAILURE);
+    CASE_IMPL(LOW_DISK_SPACE);
+    CASE_IMPL(CRASH);
+#undef CASE_IMPL
+  }
+
+  // In case of unexpected value, output the int value.
+  return os << "StopReason(" << static_cast<int>(reason) << ")";
+}
+
 }  // namespace arc