Fix csd field serializarion DCHECK in chrome://safe-browsing

Change-Id: I84d202b039ceadf48df0d1c87a49ffa40cab1fa8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2300319
Auto-Submit: Dominique Fauteux-Chapleau <domfc@chromium.org>
Reviewed-by: Roger Tawa <rogerta@chromium.org>
Reviewed-by: Daniel Rubery <drubery@chromium.org>
Commit-Queue: Daniel Rubery <drubery@chromium.org>
Cr-Commit-Position: refs/heads/master@{#788692}

components/safe_browsing/content/web_ui/safe_browsing_ui.cc

@@ -1372,9 +1372,10 @@ std::string SerializeContentAnalysisRequest(
     request_data.SetStringKey("url", request.request_data().url());
     request_data.SetStringKey("filename", request.request_data().filename());
     request_data.SetStringKey("digest", request.request_data().digest());
-    // TODO(domfc): Improve this once csd is populated for this proto.
-    request_data.SetStringKey("csd",
-                              request.request_data().csd().SerializeAsString());
+    if (request.request_data().has_csd()) {
+      request_data.SetStringKey(
+          "csd", request.request_data().csd().SerializeAsString());
+    }
     request_dict.SetKey("request_data", std::move(request_data));
   }