diff -r 000000000000 -r 6474c204b198 toolkit/components/downloads/nsDownloadProxy.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/toolkit/components/downloads/nsDownloadProxy.h	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,170 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+ 
+#ifndef downloadproxy___h___
+#define downloadproxy___h___
+
+#include "nsIDownloadManager.h"
+#include "nsIPrefBranch.h"
+#include "nsIPrefService.h"
+#include "nsIMIMEInfo.h"
+#include "nsIFileURL.h"
+#include "nsIDownloadManagerUI.h"
+
+#define PREF_BDM_SHOWWHENSTARTING "browser.download.manager.showWhenStarting"
+#define PREF_BDM_FOCUSWHENSTARTING "browser.download.manager.focusWhenStarting"
+
+// This class only exists because nsDownload cannot inherit from nsITransfer
+// directly. The reason for this is that nsDownloadManager (incorrectly) keeps
+// an nsCOMArray of nsDownloads, and nsCOMArray is only intended for use with
+// abstract classes. Using a concrete class that multiply inherits from classes
+// deriving from nsISupports will throw ambiguous base class errors.
+class nsDownloadProxy : public nsITransfer
+{
+public:
+
+  nsDownloadProxy() { }
+  virtual ~nsDownloadProxy() { }
+
+  NS_DECL_ISUPPORTS
+
+  NS_IMETHODIMP Init(nsIURI* aSource,
+                     nsIURI* aTarget,
+                     const nsAString& aDisplayName,
+                     nsIMIMEInfo *aMIMEInfo,
+                     PRTime aStartTime,
+                     nsIFile* aTempFile,
+                     nsICancelable* aCancelable,
+                     bool aIsPrivate) {
+    nsresult rv;
+    nsCOMPtr<nsIDownloadManager> dm = do_GetService("@mozilla.org/download-manager;1", &rv);
+    NS_ENSURE_SUCCESS(rv, rv);
+    
+    rv = dm->AddDownload(nsIDownloadManager::DOWNLOAD_TYPE_DOWNLOAD, aSource,
+                         aTarget, aDisplayName, aMIMEInfo, aStartTime,
+                         aTempFile, aCancelable, aIsPrivate,
+                         getter_AddRefs(mInner));
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    nsCOMPtr<nsIPrefService> prefs = do_GetService("@mozilla.org/preferences-service;1", &rv);
+    NS_ENSURE_SUCCESS(rv, rv);
+    nsCOMPtr<nsIPrefBranch> branch = do_QueryInterface(prefs);
+
+    bool showDM = true;
+    if (branch)
+      branch->GetBoolPref(PREF_BDM_SHOWWHENSTARTING, &showDM);
+
+    if (showDM) {
+      nsCOMPtr<nsIDownloadManagerUI> dmui =
+        do_GetService("@mozilla.org/download-manager-ui;1", &rv);
+      NS_ENSURE_SUCCESS(rv, rv);
+
+      bool visible;
+      rv = dmui->GetVisible(&visible);
+      NS_ENSURE_SUCCESS(rv, rv);
+
+      bool focusWhenStarting = true;
+      if (branch)
+        (void)branch->GetBoolPref(PREF_BDM_FOCUSWHENSTARTING, &focusWhenStarting);
+
+      if (visible && !focusWhenStarting)
+        return NS_OK;
+
+      return dmui->Show(nullptr, mInner, nsIDownloadManagerUI::REASON_NEW_DOWNLOAD, aIsPrivate);
+    }
+    return rv;
+  }
+
+  NS_IMETHODIMP OnStateChange(nsIWebProgress* aWebProgress,
+                              nsIRequest* aRequest, uint32_t aStateFlags,
+                              nsresult aStatus)
+  {
+    NS_ENSURE_TRUE(mInner, NS_ERROR_NOT_INITIALIZED);
+    return mInner->OnStateChange(aWebProgress, aRequest, aStateFlags, aStatus);
+  }
+  
+  NS_IMETHODIMP OnStatusChange(nsIWebProgress *aWebProgress,
+                               nsIRequest *aRequest, nsresult aStatus,
+                               const char16_t *aMessage)
+  {
+    NS_ENSURE_TRUE(mInner, NS_ERROR_NOT_INITIALIZED);
+    return mInner->OnStatusChange(aWebProgress, aRequest, aStatus, aMessage);
+  }
+
+  NS_IMETHODIMP OnLocationChange(nsIWebProgress *aWebProgress,
+                                 nsIRequest *aRequest, nsIURI *aLocation,
+                                 uint32_t aFlags)
+  {
+    NS_ENSURE_TRUE(mInner, NS_ERROR_NOT_INITIALIZED);
+    return mInner->OnLocationChange(aWebProgress, aRequest, aLocation, aFlags);
+  }
+  
+  NS_IMETHODIMP OnProgressChange(nsIWebProgress *aWebProgress,
+                                 nsIRequest *aRequest,
+                                 int32_t aCurSelfProgress,
+                                 int32_t aMaxSelfProgress,
+                                 int32_t aCurTotalProgress,
+                                 int32_t aMaxTotalProgress)
+  {
+    NS_ENSURE_TRUE(mInner, NS_ERROR_NOT_INITIALIZED);
+    return mInner->OnProgressChange(aWebProgress, aRequest,
+                                    aCurSelfProgress,
+                                    aMaxSelfProgress,
+                                    aCurTotalProgress,
+                                    aMaxTotalProgress);
+  }
+
+  NS_IMETHODIMP OnProgressChange64(nsIWebProgress *aWebProgress,
+                                   nsIRequest *aRequest,
+                                   int64_t aCurSelfProgress,
+                                   int64_t aMaxSelfProgress,
+                                   int64_t aCurTotalProgress,
+                                   int64_t aMaxTotalProgress)
+  {
+    NS_ENSURE_TRUE(mInner, NS_ERROR_NOT_INITIALIZED);
+    return mInner->OnProgressChange64(aWebProgress, aRequest,
+                                      aCurSelfProgress,
+                                      aMaxSelfProgress,
+                                      aCurTotalProgress,
+                                      aMaxTotalProgress);
+  }
+
+  NS_IMETHODIMP OnRefreshAttempted(nsIWebProgress *aWebProgress,
+                                   nsIURI *aUri,
+                                   int32_t aDelay,
+                                   bool aSameUri,
+                                   bool *allowRefresh)
+  {
+    *allowRefresh = true;
+    return NS_OK;
+  }
+
+  NS_IMETHODIMP OnSecurityChange(nsIWebProgress *aWebProgress,
+                                 nsIRequest *aRequest, uint32_t aState)
+  {
+    NS_ENSURE_TRUE(mInner, NS_ERROR_NOT_INITIALIZED);
+    return mInner->OnSecurityChange(aWebProgress, aRequest, aState);
+  }
+
+  NS_IMETHODIMP SetSha256Hash(const nsACString& aHash)
+  {
+    NS_ENSURE_TRUE(mInner, NS_ERROR_NOT_INITIALIZED);
+    return mInner->SetSha256Hash(aHash);
+  }
+
+  NS_IMETHODIMP SetSignatureInfo(nsIArray* aSignatureInfo)
+  {
+    NS_ENSURE_TRUE(mInner, NS_ERROR_NOT_INITIALIZED);
+    return mInner->SetSignatureInfo(aSignatureInfo);
+  }
+
+private:
+  nsCOMPtr<nsIDownload> mInner;
+};
+
+NS_IMPL_ISUPPORTS(nsDownloadProxy, nsITransfer,
+                  nsIWebProgressListener, nsIWebProgressListener2)
+
+#endif