Allows prefetch requests to live beyond the renderer by delaying

content/browser/loader/resource_dispatcher_host_impl.cc

Index: content/browser/loader/resource_dispatcher_host_impl.cc
diff --git a/content/browser/loader/resource_dispatcher_host_impl.cc b/content/browser/loader/resource_dispatcher_host_impl.cc
index 839678e30ce5cc01c6e57f60d725d6ef6e196d1b..160a775a5cb86619ffad124b0de42e0cf6e69017 100644
--- a/content/browser/loader/resource_dispatcher_host_impl.cc
+++ b/content/browser/loader/resource_dispatcher_host_impl.cc
@@ -127,6 +127,15 @@ const int kUserGestureWindowMs = 3500;
 // use. Arbitrarily chosen.
 const double kMaxRequestsPerProcessRatio = 0.45;
 
+bool IsDetachableResourceType(ResourceType::Type type) {
+  switch (type) {
+    case ResourceType::PREFETCH:
+      return true;
+    default:
+      return false;
+  }
+}
+
 // Aborts a request before an URLRequest has actually been created.
 void AbortRequestBeforeItStarts(ResourceMessageFilter* filter,
                                 IPC::Message* sync_result,
@@ -406,13 +415,16 @@ void ResourceDispatcherHostImpl::CancelRequestsForContext(
   for (LoaderList::iterator i = loaders_to_cancel.begin();
        i != loaders_to_cancel.end(); ++i) {
     // There is no strict requirement that this be the case, but currently
-    // downloads, streams  and transferred requests are the only requests that
-    // aren't cancelled when the associated processes go away. It may be OK for
-    // this invariant to change in the future, but if this assertion fires
-    // without the invariant changing, then it's indicative of a leak.
-    DCHECK((*i)->GetRequestInfo()->is_download() ||
-           (*i)->GetRequestInfo()->is_stream() ||
-           (*i)->is_transferring());
+    // downloads, streams, detachable requests, and transferred requests are the
+    // only requests that aren't cancelled when the associated processes go
+    // away. It may be OK for this invariant to change in the future, but if
+    // this assertion fires without the invariant changing, then it's indicative
+    // of a leak.
+    DCHECK(
+        (*i)->GetRequestInfo()->is_download() ||
+        (*i)->GetRequestInfo()->is_stream() ||
+        (*i)->GetRequestInfo()->is_detached() ||
+        (*i)->is_transferring());
   }
 #endif
 
@@ -694,18 +706,19 @@ void ResourceDispatcherHostImpl::DidReceiveRedirect(ResourceLoader* loader,
 
 void ResourceDispatcherHostImpl::DidReceiveResponse(ResourceLoader* loader) {
   ResourceRequestInfoImpl* info = loader->GetRequestInfo();
+
   // There should be an entry in the map created when we dispatched the
-  // request.
+  // request unless it's been detached and the renderer has died.
   OfflineMap::iterator policy_it(
       offline_policy_map_.find(info->GetGlobalRoutingID()));
   if (offline_policy_map_.end() != policy_it) {
     policy_it->second->UpdateStateForSuccessfullyStartedRequest(
         loader->request()->response_info());
   } else {
-    // We should always have an entry in offline_policy_map_ from when
-    // this request traversed Begin{Download,SaveFile,Request}.
+    // Unless detached, we should have an entry in offline_policy_map_ from
+    // when this request traversed Begin{Download,SaveFile,Request}.
     // TODO(rdsmith): This isn't currently true; see http://crbug.com/241176.
-    NOTREACHED();
+    DCHECK(info->is_detached());
   }
 
   int render_process_id, render_view_id;
@@ -1073,6 +1086,7 @@ void ResourceDispatcherHostImpl::BeginRequest(
           request_data.transition_type,
           false,  // is download
           false,  // is stream
+          false,  // is detachable
           allow_download,
           request_data.has_user_gesture,
           request_data.referrer_policy,
@@ -1101,6 +1115,8 @@ void ResourceDispatcherHostImpl::BeginRequest(
     handler.reset(new SyncResourceHandler(request, sync_result, this));
   } else {
     handler.reset(new AsyncResourceHandler(request, this));
+    if (IsDetachableResourceType(request_data.resource_type))
+      extra_info->set_is_detachable(true);
   }
 
   // The RedirectToFileResourceHandler depends on being next in the chain.
@@ -1219,7 +1235,8 @@ ResourceRequestInfoImpl* ResourceDispatcherHostImpl::CreateRequestInfo(
       ResourceType::SUB_RESOURCE,
       PAGE_TRANSITION_LINK,
       download,  // is_download
-      false,  // is_stream
+      false,     // is_stream
+      false,     // is_detachable
       download,  // allow_download
       false,     // has_user_gesture
       WebKit::WebReferrerPolicyDefault,
@@ -1315,8 +1332,8 @@ void ResourceDispatcherHostImpl::ResumeDeferredNavigation(
 }
 
 // The object died, so cancel and detach all requests associated with it except
-// for downloads, which belong to the browser process even if initiated via a
-// renderer.
+// for downloads and detachable resources, which belong to the browser process
+// even if initiated via a renderer.
 void ResourceDispatcherHostImpl::CancelRequestsForProcess(int child_id) {
   CancelRequestsForRoute(child_id, -1 /* cancel all */);
   registered_temp_files_.erase(child_id);
@@ -1341,14 +1358,15 @@ void ResourceDispatcherHostImpl::CancelRequestsForRoute(int child_id,
 
     GlobalRequestID id(child_id, i->first.request_id);
     DCHECK(id == i->first);
-
-    // Don't cancel navigations that are transferring to another process,
-    // since they belong to another process now.
+    // Don't cancel navigations that are expected to live beyond this process.
     if (IsTransferredNavigation(id))
       any_requests_transferring = true;
-    if (!info->is_download() && !info->is_stream() &&
-        !IsTransferredNavigation(id) &&
-        (route_id == -1 || route_id == info->GetRouteID())) {
+
+    if (info->is_detachable()) {
+      i->second->Detach();
+    } else if (!info->is_download() && !info->is_stream() &&
+               !IsTransferredNavigation(id) &&
+               (route_id == -1 || route_id == info->GetRouteID())) {
       matching_requests.push_back(id);
     }
   }