Bug 981539 - Ensure there is always a transfer object instance available in nsExternalAppHandler::OnSaveComplete for e10s. r=bz

uriloader/exthandler/nsExternalHelperAppService.cpp

@@ -2006,6 +2006,10 @@ nsExternalAppHandler::OnDataAvailable(nsIRequest *request, nsISupports * aCtxt,
 NS_IMETHODIMP nsExternalAppHandler::OnStopRequest(nsIRequest *request, nsISupports *aCtxt,
                                                   nsresult aStatus)
 {
+  LOG(("nsExternalAppHandler::OnStopRequest\n"
+       "  mCanceled=%d, mTransfer=0x%p, aStatus=0x%08X\n",
+       mCanceled, mTransfer.get(), aStatus));
+
   mStopRequestIssued = true;
 
   // Cancel if the request did not complete successfully.
@@ -2038,6 +2042,10 @@ NS_IMETHODIMP
 nsExternalAppHandler::OnSaveComplete(nsIBackgroundFileSaver *aSaver,
                                      nsresult aStatus)
 {
+  LOG(("nsExternalAppHandler::OnSaveComplete\n"
+       "  aSaver=0x%p, aStatus=0x%08X, mCanceled=%d, mTransfer=0x%p\n",
+       aSaver, aStatus, mCanceled, mTransfer.get()));
+
   if (!mCanceled) {
     // Save the hash
     (void)mSaver->GetSha256Hash(mHash);
@@ -2049,6 +2057,18 @@ nsExternalAppHandler::OnSaveComplete(nsIBackgroundFileSaver *aSaver,
     if (NS_FAILED(aStatus)) {
       nsAutoString path;
       mTempFile->GetPath(path);
+
+      // It may happen when e10s is enabled that there will be no transfer
+      // object available to communicate status as expected by the system.
+      // Let's try and create a temporary transfer object to take care of this
+      // for us, we'll fall back to using the prompt service if we absolutely
+      // have to.
+      if (!mTransfer) {
+        nsCOMPtr<nsIChannel> channel = do_QueryInterface(mRequest);
+        // We don't care if this fails.
+        CreateFailedTransfer(channel && NS_UsePrivateBrowsing(channel));
+      }
+
       SendStatusChange(kWriteError, aStatus, nullptr, path);
       if (!mCanceled)
         Cancel(aStatus);
@@ -2114,6 +2134,8 @@ NS_IMETHODIMP nsExternalAppHandler::GetSuggestedFileName(nsAString& aSuggestedFi
 
 nsresult nsExternalAppHandler::CreateTransfer()
 {
+  LOG(("nsExternalAppHandler::CreateTransfer"));
+
   MOZ_ASSERT(NS_IsMainThread(), "Must create transfer on main thread");
   // We are back from the helper app dialog (where the user chooses to save or
   // open), but we aren't done processing the load. in this case, throw up a