Allow to configure flush timeout.

Bug: 121352331
Change-Id: I99bb996a61ec24291906cac6a7fe635253de768b
diff --git a/src/tracing/core/tracing_service_impl.h b/src/tracing/core/tracing_service_impl.h
index ae4fe30..f16aaf9 100644
--- a/src/tracing/core/tracing_service_impl.h
+++ b/src/tracing/core/tracing_service_impl.h
@@ -290,6 +290,11 @@
              (base::GetWallTimeMs().count() % write_period_ms);
     }
 
+    uint32_t flush_timeout_ms() {
+      uint32_t timeout_ms = config.flush_timeout_ms();
+      return timeout_ms ? timeout_ms : kDefaultFlushTimeoutMs;
+    }
+
     const TracingSessionID id;
 
     // The consumer that started the session.