[Extensions] Add perf metrics for StartRequest()/HandleResponse()

extensions/renderer/request_sender.h

Index: extensions/renderer/request_sender.h
diff --git a/extensions/renderer/request_sender.h b/extensions/renderer/request_sender.h
index 01615641aeecad32ce0fbe01ef81ef5a6d1e7d77..5b427666a49c6b3bc0b1f434407d525a657f8ca5 100644
--- a/extensions/renderer/request_sender.h
+++ b/extensions/renderer/request_sender.h
@@ -75,7 +75,8 @@ class RequestSender {
   // TODO(koz): Remove |request_id| and generate that internally.
   //            There are multiple of these per render view though, so we'll
   //            need to vend the IDs centrally.
-  void StartRequest(Source* source,
+  // Returns true if the request is successfully sent.
+  bool StartRequest(Source* source,
                     const std::string& name,
                     int request_id,
                     bool has_callback,