Bug 1576714 - Part 4: Delay canceling original http channel during process switch, r=mattwoodrow

This patch changes when the original HttpChannelChild gets canceled during a
process switch to be after when the process switch is completed. This is needed
to prevent the load event firing too early in the original content process.

Differential Revision: https://phabricator.services.mozilla.com/D47311

--HG--
extra : moz-landing-system : lando

netwerk/protocol/http/HttpChannelParent.cpp

@@ -2104,16 +2104,6 @@ HttpChannelParent::StartRedirect(nsIChannel* newChannel, uint32_t redirectFlags,
   return NS_OK;
 }
 
-void HttpChannelParent::CancelChildCrossProcessRedirect() {
-  MOZ_ASSERT(!mDoingCrossProcessRedirect, "Already redirected");
-  MOZ_ASSERT(NS_IsMainThread());
-
-  mDoingCrossProcessRedirect = true;
-  if (!mIPCClosed) {
-    Unused << SendCancelRedirected();
-  }
-}
-
 NS_IMETHODIMP
 HttpChannelParent::CompleteRedirect(bool succeeded) {
   LOG(("HttpChannelParent::CompleteRedirect [this=%p succeeded=%d]\n", this,
@@ -2632,7 +2622,13 @@ HttpChannelParent::OnRedirectResult(bool succeeded) {
 
 nsresult HttpChannelParent::TriggerCrossProcessSwitch(nsIHttpChannel* aChannel,
                                                       uint64_t aIdentifier) {
-  CancelChildCrossProcessRedirect();
+  MOZ_ASSERT(NS_IsMainThread());
+
+  // Mark ourselves as performing a cross-process redirect. This will prevent
+  // messages being communicated to the underlying channel, allowing us to keep
+  // it open.
+  MOZ_ASSERT(!mDoingCrossProcessRedirect, "Already redirected");
+  mDoingCrossProcessRedirect = true;
 
   nsCOMPtr<nsIChannel> channel = aChannel;
   RefPtr<nsHttpChannel> httpChannel = do_QueryObject(channel);
@@ -2663,6 +2659,12 @@ nsresult HttpChannelParent::TriggerCrossProcessSwitch(nsIHttpChannel* aChannel,
       [=](uint64_t cpId) {
         nsresult rv;
 
+        // Cancel the channel in the original process, as the switch is
+        // happening in earnest.
+        if (!self->mIPCClosed) {
+          Unused << self->SendCancelRedirected();
+        }
+
         // Register the new channel and obtain id for it
         nsCOMPtr<nsIRedirectChannelRegistrar> registrar =
             RedirectChannelRegistrar::GetOrCreate();
@@ -2732,8 +2734,14 @@ nsresult HttpChannelParent::TriggerCrossProcessSwitch(nsIHttpChannel* aChannel,
                   self->CrossProcessRedirectDone(NS_ERROR_FAILURE, Nothing());
                 });
       },
-      [httpChannel](nsresult aStatus) {
+      [=](nsresult aStatus) {
         MOZ_ASSERT(NS_FAILED(aStatus), "Status should be error");
+
+        // We failed to do a process switch. Make sure the content process has
+        // canceled the channel, and then resume the load process with an error.
+        if (!self->mIPCClosed) {
+          Unused << self->SendCancelRedirected();
+        }
         httpChannel->OnRedirectVerifyCallback(aStatus);
       });
 

netwerk/protocol/http/HttpChannelParent.h

@@ -136,12 +136,6 @@ class HttpChannelParent final : public nsIInterfaceRequestor,
   nsresult TriggerCrossProcessSwitch(nsIHttpChannel* aChannel,
                                      uint64_t aIdentifier);
 
-  // Calling this method will cancel the HttpChannelChild because the consumer
-  // needs to be relocated to another process.
-  // Any OnStart/Stop/DataAvailable calls that follow will not be sent to the
-  // child channel.
-  void CancelChildCrossProcessRedirect();
-
  protected:
   // used to connect redirected-to channel in parent with just created
   // ChildChannel.  Used during redirects.