ProtocolServer: Stream the downloaded data if possible

This patchset makes ProtocolServer stream the downloads to its client
(LibProtocol), and as such changes the download API; a possible
download lifecycle could be as such:
notation = client->server:'>', server->client:'<', pipe activity:'*'
```
> StartDownload(GET, url, headers, {})
< Response(0, fd 8)
* {data, 1024b}
< HeadersBecameAvailable(0, response_headers, 200)
< DownloadProgress(0, 4K, 1024)
* {data, 1024b}
* {data, 1024b}
< DownloadProgress(0, 4K, 2048)
* {data, 1024b}
< DownloadProgress(0, 4K, 1024)
< DownloadFinished(0, true, 4K)
```

Since managing the received file descriptor is a pain, LibProtocol
implements `Download::stream_into(OutputStream)`, which can be used to
stream the download into any given output stream (be it a file, or
memory, or writing stuff with a delay, etc.).
Also, as some of the users of this API require all the downloaded data
upfront, LibProtocol also implements `set_should_buffer_all_input()`,
which causes the download instance to buffer all the data until the
download is complete, and to call the `on_buffered_download_finish`
hook.

1 files changed, 2 insertions, 2 deletions

diff --git a/Applications/Browser/main.cpp b/Applications/Browser/main.cpp
index 3624ca6076..07b79ed505 100644
--- a/Applications/Browser/main.cpp
+++ b/Applications/Browser/main.cpp
@@ -68,7 +68,7 @@ int main(int argc, char** argv)
         return 1;
     }
 
-    if (pledge("stdio shared_buffer accept unix cpath rpath wpath fattr", nullptr) < 0) {
+    if (pledge("stdio shared_buffer accept unix cpath rpath wpath fattr sendfd recvfd", nullptr) < 0) {
         perror("pledge");
         return 1;
     }
@@ -86,7 +86,7 @@ int main(int argc, char** argv)
     Web::ResourceLoader::the();
 
     // FIXME: Once there is a standalone Download Manager, we can drop the "unix" pledge.
-    if (pledge("stdio shared_buffer accept unix cpath rpath wpath", nullptr) < 0) {
+    if (pledge("stdio shared_buffer accept unix cpath rpath wpath sendfd recvfd", nullptr) < 0) {
         perror("pledge");
         return 1;
     }