Bug 1681529 - Part 5: Serialize `nsIInputStream` over IPC with aDelayedStart by default, r=baku

The current set of cases where a nsIInputStream is directly serialized over IPC
is fairly limited, and includes cases where the IPDL struct may be directly
stored within a content process, having the nsIInputStream left unused.

By switching this serialization to DelayedStart, we can avoid performing
unnecessary streaming copies of IPC data when sending postdata streams related
to session history and document navigation, while also avoiding issues like this
coming up again due to delayed start being the default.

Differential Revision: https://phabricator.services.mozilla.com/D101804

ipc/glue/IPCStreamUtils.cpp

@@ -551,7 +551,7 @@ Maybe<IPCStream>& AutoIPCStream::TakeOptionalValue() {
 void IPDLParamTraits<nsIInputStream*>::Write(IPC::Message* aMsg,
                                              IProtocol* aActor,
                                              nsIInputStream* aParam) {
-  auto autoStream = MakeRefPtr<HoldIPCStream>();
+  auto autoStream = MakeRefPtr<HoldIPCStream>(/* aDelayedStart */ true);
 
   bool ok = false;
   bool found = false;

ipc/glue/IPCStreamUtils.h

@@ -200,6 +200,8 @@ class HoldIPCStream final : public AutoIPCStream {
  public:
   NS_INLINE_DECL_REFCOUNTING(HoldIPCStream)
 
+  using AutoIPCStream::AutoIPCStream;
+
  private:
   ~HoldIPCStream() = default;
 };