Reland "[Prefetch]: DCHECK if recursive prefetch token is set incorrectly"

This reverts commit 2638a6e6.

Reason for revert: We thought we had collected enough crash data, however crbug.com/1122182 was not actually fixed yet, so the minidumps did not actually contain the information we needed. agrieve@ has informed me that the issue should be fixed now, and we'll confirm whether or not that is the case by:
 1.) Reverting this change
 2.) Collecting minidumps
 3.) Examining the minidumps to confirm that the debugging information exists

Original change's description:
> Revert "[Prefetch]: DCHECK if recursive prefetch token is set incorrectly"
>
> This reverts commit b344652b.
> Reason for revert: We have collected enough crashdumps now, and this is
> causing crash metrics to be skewed as it's getting counted as a real
> crash.
>
> Bug: 1132770
> Change-Id: Ia2e7a92bea2ebeca01c62ca9af73d3fe014685f6
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2505985
> Auto-Submit: Mugdha Lakhani <nator@chromium.org>
> Commit-Queue: Charlie Harrison <csharrison@chromium.org>
> Reviewed-by: Charlie Harrison <csharrison@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#822189}

TBR=csharrison@chromium.org,nator@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

TBR: charrison@chromium.org
Bug: 1132770
Change-Id: I31ac96c2c5f4f0738fd2d8c4e60236b2bc0c35a3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2513109Reviewed-by: Charlie Harrison <csharrison@chromium.org>
Reviewed-by: Mugdha Lakhani <nator@chromium.org>
Reviewed-by: Dominic Farolino <dom@chromium.org>
Commit-Queue: Dominic Farolino <dom@chromium.org>
Cr-Commit-Position: refs/heads/master@{#829091}

content/browser/loader/prefetch_url_loader_service.cc

@@ -5,6 +5,7 @@
 #include "content/browser/loader/prefetch_url_loader_service.h"
 
 #include "base/bind.h"
+#include "base/debug/dump_without_crashing.h"
 #include "base/feature_list.h"
 #include "base/time/default_tick_clock.h"
 #include "content/browser/loader/prefetch_url_loader.h"
@@ -28,6 +29,14 @@
 #include "third_party/blink/public/common/renderer_preferences/renderer_preferences.h"
 #include "third_party/blink/public/mojom/loader/resource_load_info.mojom-shared.h"
 
+namespace {
+void DumpWithoutCrashing(const network::ResourceRequest& request) {
+  DEBUG_ALIAS_FOR_GURL(prefetch_buf, request.url);
+  DEBUG_ALIAS_FOR_GURL(initiator_buf, request.request_initiator->GetURL());
+  base::debug::DumpWithoutCrashing();
+}
+}  // namespace
+
 namespace content {
 
 struct PrefetchURLLoaderService::BindContext {
@@ -162,9 +171,18 @@ void PrefetchURLLoaderService::CreateLoaderAndStart(
 
   // Recursive prefetch from a cross-origin main resource prefetch.
   if (resource_request.recursive_prefetch_token) {
-    // TODO(crbug.com/1123715): Figure out why we're seeing this condition hold
-    // true in the field.
+    // A request's |recursive_prefetch_token| is only provided if the request is
+    // a recursive prefetch. This means it is expected that the current
+    // context's |cross_origin_factory| was already created.
     if (!current_context.cross_origin_factory) {
+      // This could happen due to a compromised renderer passing in a recursive
+      // prefetch token for a request that's not a recursive prefetch. Cancel
+      // the request.
+      DVLOG(1) << "Recursive prefetch token unexpectedly set.";
+      DumpWithoutCrashing(resource_request);
+      mojo::Remote<network::mojom::URLLoaderClient>(std::move(client))
+          ->OnComplete(
+              network::URLLoaderCompletionStatus(net::ERR_INVALID_ARGUMENT));
       return;
     }
 
@@ -178,6 +196,8 @@ void PrefetchURLLoaderService::CreateLoaderAndStart(
     // a request in a special way. We'll cancel the request.
     if (isolation_info_iterator ==
         current_context.prefetch_isolation_infos.end()) {
+      DVLOG(1) << "Recursive prefetch request is missing prefetch isolation";
+      DumpWithoutCrashing(resource_request);
       mojo::Remote<network::mojom::URLLoaderClient>(std::move(client))
           ->OnComplete(
               network::URLLoaderCompletionStatus(net::ERR_INVALID_ARGUMENT));