Correctly record and pass around navigation start time.

mojo/services/network/public/interfaces/url_loader.mojom

Index: mojo/services/network/public/interfaces/url_loader.mojom
diff --git a/mojo/services/network/public/interfaces/url_loader.mojom b/mojo/services/network/public/interfaces/url_loader.mojom
index f9601099fd71a6cd9cf1c71073402fb3db6315d5..8a18c2605a6741db1a36ef4989131a1da63a3cac 100644
--- a/mojo/services/network/public/interfaces/url_loader.mojom
+++ b/mojo/services/network/public/interfaces/url_loader.mojom
@@ -35,6 +35,9 @@ struct URLRequest {
   // servers to also not satisfy the request from their cache.  This has the
   // effect of forcing a full end-to-end fetch.
   bool bypass_cache = false;
+
+  // The time when this request originated. 0 indicates that it is not recorded.
+  int64 originating_time_ticks = 0;
 };
 
 struct URLResponse {