ServiceWorker: Use mojo's data pipe for respondWith(stream)

content/common/service_worker/service_worker_event_dispatcher.mojom

Index: content/common/service_worker/service_worker_event_dispatcher.mojom
diff --git a/content/common/service_worker/service_worker_event_dispatcher.mojom b/content/common/service_worker/service_worker_event_dispatcher.mojom
index 2f309bb3bd2729fcd745f61b71b0c43a55cd34f3..cc016bae821bf61095bd6544a8289ad8f924c116 100644
--- a/content/common/service_worker/service_worker_event_dispatcher.mojom
+++ b/content/common/service_worker/service_worker_event_dispatcher.mojom
@@ -11,6 +11,7 @@ import "mojo/common/time.mojom";
 import "third_party/WebKit/public/platform/modules/background_sync/background_sync.mojom";
 import "third_party/WebKit/public/platform/modules/fetch/fetch_api_request.mojom";
 import "third_party/WebKit/public/platform/modules/serviceworker/service_worker_event_status.mojom";
+import "third_party/WebKit/public/platform/modules/serviceworker/service_worker_stream_handle.mojom";
 import "url/mojo/origin.mojom";
 
 [Native]
@@ -50,6 +51,20 @@ struct ExtendableMessageEvent {
   ExtendableMessageEventSource source;
 };
 
+// Browser-side interface which is passed through DispatchFetchEvent.

[falken, 2017/04/10 01:21:57]

In addition to "browser-side interface", the comment could explain what the
interface is for. "The renderer uses this interface to respond to a fetch
event."

[shimazu, 2017/04/11 01:32:57]

Done.

+// The legacy IPC is used when the response body is using blob storage due to
+// the IPC's ordering issue.

[falken, 2017/04/10 01:21:57]

It's a little hard to tell in which cases this interface is used vs in which
cases the legacy IPC is used. Suggest:
"This interface is only used for responses where the body is a stream. The
legacy IPC is used instead when..."

"The IPC's ordering issue" is a bit vague. 

Are the only response types blob and stream? What happens in
respondWith(preloadResponse)?

[shimazu, 2017/04/11 01:32:57]

Done.

+// TODO(shimazu): Use this interface for all responses after the blob system is
+// mojoified: https://crbug.com/611935.
+interface ServiceWorkerFetchResponseCallback {
+  OnResponse(ServiceWorkerResponse response,
+             mojo.common.mojom.Time dispatch_event_time);
+  OnResponseStream(ServiceWorkerResponse response,
+                   blink.mojom.ServiceWorkerStreamHandle stream_handle,
+                   mojo.common.mojom.Time dispatch_event_time);
+  OnFallback(mojo.common.mojom.Time dispatch_event_time);
+};
+
 // Renderer-side interface bound to ServiceWorkerContextClient for dispatching
 // events.
 // Those events expecting such response
@@ -77,7 +92,8 @@ interface ServiceWorkerEventDispatcher {
   // |fetch_event_id| is used internally when sending the response back to the
   // browser process.
   DispatchFetchEvent(int32 fetch_event_id, blink.mojom.FetchAPIRequest request,
-                     FetchEventPreloadHandle? preload_handle)
+                     FetchEventPreloadHandle? preload_handle,
+                     ServiceWorkerFetchResponseCallback response_callback)
       => (blink.mojom.ServiceWorkerEventStatus status,
           mojo.common.mojom.Time dispatch_event_time);
   DispatchNotificationClickEvent(string notification_id,