components: Add out-of-line copy ctors for complex classes.

components/device_event_log/device_event_log_impl.h

Index: components/device_event_log/device_event_log_impl.h
diff --git a/components/device_event_log/device_event_log_impl.h b/components/device_event_log/device_event_log_impl.h
index f221638e95d6155ab2f0a80bbf33e5fb1b694fb3..218a2e7ff22a6781b13ea791151d34b201a13d3d 100644
--- a/components/device_event_log/device_event_log_impl.h
+++ b/components/device_event_log/device_event_log_impl.h
@@ -28,6 +28,7 @@ class DEVICE_EVENT_LOG_EXPORT DeviceEventLogImpl {
              LogType log_type,
              LogLevel log_level,
              const std::string& event);
+    LogEntry(const LogEntry& other);
 
     std::string file;
     int file_line;