Relax DCHECKs regarding Threads and RefCounts in iOS' HttpServer.

ios/web/public/test/http_server.mm

Index: ios/web/public/test/http_server.mm
diff --git a/ios/web/public/test/http_server.mm b/ios/web/public/test/http_server.mm
index c5217160571ec5b3fd3ce695aa0c8500d613e35a..b5789f4a0328fe83c85133b2ab5a7b418e9188e7 100644
--- a/ios/web/public/test/http_server.mm
+++ b/ios/web/public/test/http_server.mm
@@ -9,6 +9,7 @@
 #include <string>
 
 #include "base/logging.h"
+#include "base/memory/ref_counted.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/sys_string_conversions.h"
 #import "ios/third_party/gcdwebserver/src/GCDWebServer/Core/GCDWebServer.h"
@@ -80,6 +81,11 @@ void HttpServer::InitHttpServer() {
   // Note: This block is called from an arbitrary GCD thread.
   id process_request =
       ^GCDWebServerResponse*(GCDWebServerDataRequest* request) {
+      // Relax the cross-thread access restriction to non-thread-safe RefCount.
+      // TODO(crbug.com/707010): Remove ScopedAllowCrossThreadRefCountAccess.
+      base::ScopedAllowCrossThreadRefCountAccess
+          allow_cross_thread_ref_count_access;
+
       ResponseProvider::Request provider_request =
           ResponseProviderRequestFromGCDWebServerRequest(request);
       scoped_refptr<RefCountedResponseProviderWrapper>
@@ -183,6 +189,10 @@ scoped_refptr<RefCountedResponseProviderWrapper>
     HttpServer::GetResponseProviderForRequest(
         const web::ResponseProvider::Request& request) {
   base::AutoLock autolock(provider_list_lock_);
+  // Relax the cross-thread access restriction to non-thread-safe RefCount.
+  // The lock above protects non-thread-safe RefCount in HTTPServer.
+  base::ScopedAllowCrossThreadRefCountAccess
+      allow_cross_thread_ref_count_access;
   scoped_refptr<RefCountedResponseProviderWrapper> result;
   for (const auto& ref_counted_response_provider : providers_) {
     ResponseProvider* response_provider =
@@ -202,6 +212,10 @@ void HttpServer::AddResponseProvider(
   DCHECK(IsRunning()) << "Can add a response provider only when the server is "
                       << "running.";
   base::AutoLock autolock(provider_list_lock_);
+  // Relax the cross-thread access restriction to non-thread-safe RefCount.
+  // The lock above protects non-thread-safe RefCount in HTTPServer.
+  base::ScopedAllowCrossThreadRefCountAccess
+      allow_cross_thread_ref_count_access;
   scoped_refptr<RefCountedResponseProviderWrapper>
       ref_counted_response_provider(
           new RefCountedResponseProviderWrapper(std::move(response_provider)));
@@ -211,6 +225,10 @@ void HttpServer::AddResponseProvider(
 void HttpServer::RemoveResponseProvider(ResponseProvider* response_provider) {
   DCHECK([NSThread isMainThread]);
   base::AutoLock autolock(provider_list_lock_);
+  // Relax the cross-thread access restriction to non-thread-safe RefCount.
+  // The lock above protects non-thread-safe RefCount in HTTPServer.
+  base::ScopedAllowCrossThreadRefCountAccess
+      allow_cross_thread_ref_count_access;
   auto found_iter = providers_.end();
   for (auto it = providers_.begin(); it != providers_.end(); ++it) {
     if ((*it)->GetResponseProvider() == response_provider) {
@@ -226,6 +244,10 @@ void HttpServer::RemoveResponseProvider(ResponseProvider* response_provider) {
 void HttpServer::RemoveAllResponseProviders() {
   DCHECK([NSThread isMainThread]);
   base::AutoLock autolock(provider_list_lock_);
+  // Relax the cross-thread access restriction to non-thread-safe RefCount.
+  // The lock above protects non-thread-safe RefCount in HTTPServer.
+  base::ScopedAllowCrossThreadRefCountAccess
+      allow_cross_thread_ref_count_access;
   providers_.clear();
 }