DumpWithoutCrashing when trust token params deserialization fails

crbug.com/1062637 reported URLLoaderFactory
VALIDATION_ERROR_DESERIALIZATION_FAILED crashes starting shortly after
adding a new member to ResourceRequest. The new member, of type
OptionalTrustTokenParams, is only used for functionality currently
behind a flag (and not enabled anywhere in production).

To help diagnose the cause of the crash (and, in particular, whether
it has to do with the trust_token_params field) this change separates
the deserialization of this field from the large "if (!Read(A) ||
!Read(B) || ...)" conditional in url_request_mojom_traits.cc and
specifically dumps on failure to deserialize the field.

R=yhirano

Bug: 1062637
Change-Id: Icc199fe29bcf1179d762971fb383ffee95b31ee9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2119764
Commit-Queue: David Van Cleve <davidvc@chromium.org>
Reviewed-by: Matthew Denton <mpdenton@chromium.org>
Reviewed-by: Yutaka Hirano <yhirano@chromium.org>
Cr-Commit-Position: refs/heads/master@{#754090}

services/network/public/cpp/url_request_mojom_traits.cc

@@ -6,6 +6,7 @@
 
 #include <vector>
 
+#include "base/debug/dump_without_crashing.h"
 #include "base/logging.h"
 #include "mojo/public/cpp/base/file_mojom_traits.h"
 #include "mojo/public/cpp/base/file_path_mojom_traits.h"
@@ -187,11 +188,19 @@ bool StructTraits<
       !data.ReadThrottlingProfileId(&out->throttling_profile_id) ||
       !data.ReadFetchWindowId(&out->fetch_window_id) ||
       !data.ReadDevtoolsRequestId(&out->devtools_request_id) ||
-      !data.ReadRecursivePrefetchToken(&out->recursive_prefetch_token) ||
-      !data.ReadTrustTokenParams(&out->trust_token_params.as_ptr())) {
+      !data.ReadRecursivePrefetchToken(&out->recursive_prefetch_token)) {
+    // Note that data.ReadTrustTokenParams is temporarily handled below.
     return false;
   }
 
+  // Temporarily separated from the remainder of the deserialization in order to
+  // help debug crbug.com/1062637.
+  if (!data.ReadTrustTokenParams(&out->trust_token_params.as_ptr())) {
+    // We don't return false here to avoid duplicate reports.
+    out->trust_token_params = base::nullopt;
+    base::debug::DumpWithoutCrashing();
+  }
+
   out->attach_same_site_cookies = data.attach_same_site_cookies();
   out->update_first_party_url_on_redirect =
       data.update_first_party_url_on_redirect();