Add DCHECKs to validate ProfileIOData's list of protocols.

content/browser/storage_partition_impl_map.cc

Index: content/browser/storage_partition_impl_map.cc
diff --git a/content/browser/storage_partition_impl_map.cc b/content/browser/storage_partition_impl_map.cc
index 0e85d8a6238f7fab568733139fc376d4fcbf04a0..1ab960991f634826904d5794ba38f669ddb10263 100644
--- a/content/browser/storage_partition_impl_map.cc
+++ b/content/browser/storage_partition_impl_map.cc
@@ -169,6 +169,14 @@ base::FilePath GetStoragePartitionDomainPath(
       .Append(base::FilePath::FromUTF8Unsafe(partition_domain));
 }
 
+#if DCHECK_IS_ON()
+bool IsBuiltInProtocol(const std::string& scheme) {
+  GURL scheme_as_gurl(scheme + url::kStandardSchemeSeparator);
+  DCHECK(scheme_as_gurl.is_valid()) << scheme;
+  return GetContentClient()->browser()->IsHandledURL(scheme_as_gurl);
+}
+#endif
+
 // Helper function for doing a depth-first deletion of the data on disk.
 // Examines paths directly in |current_dir| (no recursion) and tries to
 // delete from disk anything that is in, or isn't a parent of something in
@@ -436,11 +444,19 @@ StoragePartitionImpl* StoragePartitionImplMap::Get(
                 browser_context_->IsOffTheRecord(),
                 blob_storage_context).release());
   }
+
   protocol_handlers[kChromeDevToolsScheme] =
       linked_ptr<net::URLRequestJobFactory::ProtocolHandler>(
           CreateDevToolsProtocolHandler(browser_context_->GetResourceContext(),
                                         browser_context_->IsOffTheRecord()));
 
+#if DCHECK_IS_ON()
+  // The ContentBrowserClient's implementation of IsHandledURL must know about
+  // all protocols handled by the content layer.
+  for (const auto& handler : protocol_handlers)
+    DCHECK(IsBuiltInProtocol(handler.first)) << handler.first;
+#endif  // DCHECK_IS_ON()
+
   URLRequestInterceptorScopedVector request_interceptors;
   request_interceptors.push_back(
       ServiceWorkerRequestHandler::CreateInterceptor(