Bug 1430508: Return 0 for ProcessId() when channel IPC is closed. r=dragana

There are some corner cases where we try to attach StreamFilter endpoints to a
channel after its IPC has been closed from from the other side, but request
listeners haven't been notified. This causes crashes in any of several places.

This patch changes nsHttpChannel::ProcessId to return 0 when IPC is closed, so
callers can detect that it's no longer possible to attach endpoints to it.

MozReview-Commit-ID: BZTOqezih0P

--HG--
extra : rebase_source : dfdb5bf7a11fccea51a1fbb161e688f10167da30

netwerk/protocol/http/HttpChannelParent.cpp

@@ -265,6 +265,15 @@ HttpChannelParent::CleanupBackgroundChannel()
   }
 }
 
+base::ProcessId
+HttpChannelParent::OtherPid() const
+{
+  if (mIPCClosed) {
+    return 0;
+  }
+  return Manager()->OtherPid();
+}
+
 //-----------------------------------------------------------------------------
 // HttpChannelParent::nsISupports
 //-----------------------------------------------------------------------------

netwerk/protocol/http/HttpChannelParent.h

@@ -120,6 +120,8 @@ public:
   // Callback while background channel is destroyed.
   void OnBackgroundParentDestroyed();
 
+  base::ProcessId OtherPid() const override;
+
 protected:
   // used to connect redirected-to channel in parent with just created
   // ChildChannel.  Used during redirects.

toolkit/components/extensions/webrequest/StreamFilterParent.cpp

@@ -136,9 +136,12 @@ StreamFilterParent::Create(dom::ContentParent* aContentParent, uint64_t aChannel
   RefPtr<nsHttpChannel> chan = do_QueryObject(channel);
   NS_ENSURE_TRUE(chan, false);
 
+  auto channelPid = chan->ProcessId();
+  NS_ENSURE_TRUE(channelPid, false);
+
   Endpoint<PStreamFilterParent> parent;
   Endpoint<PStreamFilterChild> child;
-  nsresult rv = PStreamFilter::CreateEndpoints(chan->ProcessId(),
+  nsresult rv = PStreamFilter::CreateEndpoints(channelPid,
                                                aContentParent ? aContentParent->OtherPid()
                                                               : base::GetCurrentProcId(),
                                                &parent, &child);