Adding upstream version 124.0.1.upstream/124.0.1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

4 files changed, 1677 insertions, 0 deletions

diff --git a/uriloader/exthandler/win/nsMIMEInfoWin.cpp b/uriloader/exthandler/win/nsMIMEInfoWin.cpp
new file mode 100644
index 0000000000..758b2018a7
--- /dev/null
+++ b/uriloader/exthandler/win/nsMIMEInfoWin.cpp
@@ -0,0 +1,913 @@
+/* -*- Mode: C++; tab-width: 3; 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/. */
+
+#include "nsArrayEnumerator.h"
+#include "nsComponentManagerUtils.h"
+#include "nsCOMArray.h"
+#include "nsLocalFile.h"
+#include "nsMIMEInfoWin.h"
+#include "nsIMIMEService.h"
+#include "nsNetUtil.h"
+#include <windows.h>
+#include <shellapi.h>
+#include "nsIMutableArray.h"
+#include "nsTArray.h"
+#include <shlobj.h>
+#include "nsIWindowsRegKey.h"
+#include "nsUnicharUtils.h"
+#include "nsTextToSubURI.h"
+#include "nsVariant.h"
+#include "mozilla/CmdLineAndEnvUtils.h"
+#include "mozilla/ShellHeaderOnlyUtils.h"
+#include "mozilla/StaticPrefs_browser.h"
+#include "mozilla/UrlmonHeaderOnlyUtils.h"
+#include "mozilla/UniquePtrExtensions.h"
+
+#define RUNDLL32_EXE L"\\rundll32.exe"
+
+NS_IMPL_ISUPPORTS_INHERITED(nsMIMEInfoWin, nsMIMEInfoBase, nsIPropertyBag)
+
+nsMIMEInfoWin::~nsMIMEInfoWin() {}
+
+nsresult nsMIMEInfoWin::LaunchDefaultWithFile(nsIFile* aFile) {
+  // Launch the file, unless it is an executable.
+  bool executable = true;
+  aFile->IsExecutable(&executable);
+  if (executable) return NS_ERROR_FAILURE;
+
+  return aFile->Launch();
+}
+
+nsresult nsMIMEInfoWin::ShellExecuteWithIFile(nsIFile* aExecutable, int aArgc,
+                                              const wchar_t** aArgv) {
+  nsresult rv;
+
+  NS_ASSERTION(aArgc >= 1, "aArgc must be at least 1");
+
+  nsAutoString execPath;
+  rv = aExecutable->GetTarget(execPath);
+  if (NS_FAILED(rv) || execPath.IsEmpty()) {
+    rv = aExecutable->GetPath(execPath);
+  }
+  if (NS_FAILED(rv)) {
+    return rv;
+  }
+
+  auto assembledArgs = mozilla::MakeCommandLine(aArgc, aArgv);
+  if (!assembledArgs) {
+    return NS_ERROR_FILE_EXECUTION_FAILED;
+  }
+
+  _bstr_t execPathBStr(execPath.get());
+  // Pass VT_ERROR/DISP_E_PARAMNOTFOUND to omit an optional RPC parameter
+  // to execute a file with the default verb.
+  _variant_t verbDefault(DISP_E_PARAMNOTFOUND, VT_ERROR);
+  _variant_t workingDir;
+  _variant_t showCmd(SW_SHOWNORMAL);
+
+  // Ask Explorer to ShellExecute on our behalf, as some applications such as
+  // Skype for Business do not start correctly when inheriting our process's
+  // migitation policies.
+  // It does not work in a special environment such as Citrix.  In such a case
+  // we fall back to launching an application as a child process.  We need to
+  // find a way to handle the combination of these interop issues.
+  mozilla::LauncherVoidResult shellExecuteOk = mozilla::ShellExecuteByExplorer(
+      execPathBStr, assembledArgs.get(), verbDefault, workingDir, showCmd);
+  if (shellExecuteOk.isErr()) {
+    // No need to pass assembledArgs to LaunchWithIProcess.  aArgv will be
+    // processed in nsProcess::RunProcess.
+    return LaunchWithIProcess(aExecutable, aArgc,
+                              reinterpret_cast<const char16_t**>(aArgv));
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsMIMEInfoWin::LaunchWithFile(nsIFile* aFile) {
+  nsresult rv;
+
+  // it doesn't make any sense to call this on protocol handlers
+  NS_ASSERTION(mClass == eMIMEInfo,
+               "nsMIMEInfoBase should have mClass == eMIMEInfo");
+
+  if (AutomationOnlyCheckIfLaunchStubbed(aFile)) {
+    return NS_OK;
+  }
+
+  if (mPreferredAction == useSystemDefault) {
+    nsCOMPtr<nsIFile> defaultApp = GetDefaultApplication();
+    if (defaultApp &&
+        mozilla::StaticPrefs::browser_pdf_launchDefaultEdgeAsApp()) {
+      // Since Edgium is the default handler for PDF and other kinds of files,
+      // if we're using the OS default and it's Edgium prefer its app mode so it
+      // operates as a viewer (without browser toolbars). Bug 1632277.
+      nsAutoCString defaultAppExecutable;
+      rv = defaultApp->GetNativeLeafName(defaultAppExecutable);
+      if (NS_SUCCEEDED(rv) &&
+          defaultAppExecutable.LowerCaseEqualsLiteral("msedge.exe")) {
+        nsAutoString path;
+        rv = aFile->GetPath(path);
+        if (NS_SUCCEEDED(rv)) {
+          // If the --app flag doesn't work we'll want to fallback to a
+          // regular path. Send two args so we call `msedge.exe --app={path}
+          // {path}`.
+          nsAutoString appArg;
+          appArg.AppendLiteral("--app=");
+          appArg.Append(path);
+          const wchar_t* argv[] = {appArg.get(), path.get()};
+
+          return ShellExecuteWithIFile(defaultApp, mozilla::ArrayLength(argv),
+                                       argv);
+        }
+      }
+    }
+    return LaunchDefaultWithFile(aFile);
+  }
+
+  if (mPreferredAction == useHelperApp) {
+    if (!mPreferredApplication) return NS_ERROR_FILE_NOT_FOUND;
+
+    // at the moment, we only know how to hand files off to local handlers
+    nsCOMPtr<nsILocalHandlerApp> localHandler =
+        do_QueryInterface(mPreferredApplication, &rv);
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    nsCOMPtr<nsIFile> executable;
+    rv = localHandler->GetExecutable(getter_AddRefs(executable));
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    // Deal with local dll based handlers
+    nsCString filename;
+    executable->GetNativeLeafName(filename);
+    if (filename.Length() > 4) {
+      nsCString extension(Substring(filename, filename.Length() - 4, 4));
+
+      if (extension.LowerCaseEqualsLiteral(".dll")) {
+        nsAutoString args;
+
+        // executable is rundll32, everything else is a list of parameters,
+        // including the dll handler.
+        if (!GetDllLaunchInfo(executable, aFile, args, false))
+          return NS_ERROR_INVALID_ARG;
+
+        WCHAR rundll32Path[MAX_PATH + sizeof(RUNDLL32_EXE) / sizeof(WCHAR) +
+                           1] = {L'\0'};
+        if (!GetSystemDirectoryW(rundll32Path, MAX_PATH)) {
+          return NS_ERROR_FILE_NOT_FOUND;
+        }
+        lstrcatW(rundll32Path, RUNDLL32_EXE);
+
+        SHELLEXECUTEINFOW seinfo;
+        memset(&seinfo, 0, sizeof(seinfo));
+        seinfo.cbSize = sizeof(SHELLEXECUTEINFOW);
+        seinfo.fMask = 0;
+        seinfo.hwnd = nullptr;
+        seinfo.lpVerb = nullptr;
+        seinfo.lpFile = rundll32Path;
+        seinfo.lpParameters = args.get();
+        seinfo.lpDirectory = nullptr;
+        seinfo.nShow = SW_SHOWNORMAL;
+        if (ShellExecuteExW(&seinfo)) return NS_OK;
+
+        switch ((LONG_PTR)seinfo.hInstApp) {
+          case 0:
+          case SE_ERR_OOM:
+            return NS_ERROR_OUT_OF_MEMORY;
+          case SE_ERR_ACCESSDENIED:
+            return NS_ERROR_FILE_ACCESS_DENIED;
+          case SE_ERR_ASSOCINCOMPLETE:
+          case SE_ERR_NOASSOC:
+            return NS_ERROR_UNEXPECTED;
+          case SE_ERR_DDEBUSY:
+          case SE_ERR_DDEFAIL:
+          case SE_ERR_DDETIMEOUT:
+            return NS_ERROR_NOT_AVAILABLE;
+          case SE_ERR_DLLNOTFOUND:
+            return NS_ERROR_FAILURE;
+          case SE_ERR_SHARE:
+            return NS_ERROR_FILE_IS_LOCKED;
+          default:
+            switch (GetLastError()) {
+              case ERROR_FILE_NOT_FOUND:
+                return NS_ERROR_FILE_NOT_FOUND;
+              case ERROR_PATH_NOT_FOUND:
+                return NS_ERROR_FILE_UNRECOGNIZED_PATH;
+              case ERROR_BAD_FORMAT:
+                return NS_ERROR_FILE_CORRUPTED;
+            }
+        }
+        return NS_ERROR_FILE_EXECUTION_FAILED;
+      }
+    }
+    nsAutoString path;
+    aFile->GetPath(path);
+    const wchar_t* argv[] = {path.get()};
+    return ShellExecuteWithIFile(executable, mozilla::ArrayLength(argv), argv);
+  }
+
+  return NS_ERROR_INVALID_ARG;
+}
+
+NS_IMETHODIMP
+nsMIMEInfoWin::GetHasDefaultHandler(bool* _retval) {
+  // We have a default application if we have a description
+  // We can ShellExecute anything; however, callers are probably interested if
+  // there is really an application associated with this type of file
+  *_retval = !mDefaultAppDescription.IsEmpty();
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsMIMEInfoWin::GetEnumerator(nsISimpleEnumerator** _retval) {
+  nsCOMArray<nsIVariant> properties;
+
+  nsCOMPtr<nsIVariant> variant;
+  GetProperty(u"defaultApplicationIconURL"_ns, getter_AddRefs(variant));
+  if (variant) properties.AppendObject(variant);
+
+  GetProperty(u"customApplicationIconURL"_ns, getter_AddRefs(variant));
+  if (variant) properties.AppendObject(variant);
+
+  return NS_NewArrayEnumerator(_retval, properties, NS_GET_IID(nsIVariant));
+}
+
+static nsresult GetIconURLVariant(nsIFile* aApplication, nsIVariant** _retval) {
+  nsAutoCString fileURLSpec;
+  NS_GetURLSpecFromFile(aApplication, fileURLSpec);
+  nsAutoCString iconURLSpec;
+  iconURLSpec.AssignLiteral("moz-icon://");
+  iconURLSpec += fileURLSpec;
+  RefPtr<nsVariant> writable(new nsVariant());
+  writable->SetAsAUTF8String(iconURLSpec);
+  writable.forget(_retval);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsMIMEInfoWin::GetProperty(const nsAString& aName, nsIVariant** _retval) {
+  nsresult rv;
+  nsCOMPtr<nsIFile> defaultApp = GetDefaultApplication();
+  if (defaultApp && aName.EqualsLiteral(PROPERTY_DEFAULT_APP_ICON_URL)) {
+    rv = GetIconURLVariant(defaultApp, _retval);
+    NS_ENSURE_SUCCESS(rv, rv);
+  } else if (mPreferredApplication &&
+             aName.EqualsLiteral(PROPERTY_CUSTOM_APP_ICON_URL)) {
+    nsCOMPtr<nsILocalHandlerApp> localHandler =
+        do_QueryInterface(mPreferredApplication, &rv);
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    nsCOMPtr<nsIFile> executable;
+    rv = localHandler->GetExecutable(getter_AddRefs(executable));
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    rv = GetIconURLVariant(executable, _retval);
+    NS_ENSURE_SUCCESS(rv, rv);
+  }
+
+  return NS_OK;
+}
+
+// this implementation was pretty much copied verbatime from
+// Tony Robinson's code in nsExternalProtocolWin.cpp
+nsresult nsMIMEInfoWin::LoadUriInternal(nsIURI* aURL) {
+  nsresult rv = NS_OK;
+
+  // 1. Find the default app for this protocol
+  // 2. Set up the command line
+  // 3. Launch the app.
+
+  // For now, we'll just cheat essentially, check for the command line
+  // then just call ShellExecute()!
+
+  if (aURL) {
+    // extract the url spec from the url
+    nsAutoCString urlSpec;
+    aURL->GetAsciiSpec(urlSpec);
+
+    // Unescape non-ASCII characters in the URL
+    nsAutoString utf16Spec;
+    if (NS_FAILED(nsTextToSubURI::UnEscapeNonAsciiURI("UTF-8"_ns, urlSpec,
+                                                      utf16Spec))) {
+      CopyASCIItoUTF16(urlSpec, utf16Spec);
+    }
+
+    // Ask the shell/urlmon to parse |utf16Spec| to avoid malformed URLs.
+    // Failure is indicative of a potential security issue so we should
+    // bail out if so.
+    mozilla::LauncherResult<_bstr_t> validatedUri =
+        mozilla::UrlmonValidateUri(utf16Spec.get());
+    if (validatedUri.isErr()) {
+      return NS_ERROR_FAILURE;
+    }
+
+    _variant_t args;
+    _variant_t verb(L"open");
+    _variant_t workingDir;
+    _variant_t showCmd(SW_SHOWNORMAL);
+
+    // To open a uri, we first try ShellExecuteByExplorer, which starts a new
+    // process as a child process of explorer.exe, because applications may not
+    // support the mitigation policies inherited from our process.  If it fails,
+    // we fall back to ShellExecuteExW.
+    //
+    // For Thunderbird, however, there is a known issue that
+    // ShellExecuteByExplorer succeeds but explorer.exe shows an error popup
+    // if a uri to open includes credentials.  This does not happen in Firefox
+    // because Firefox does not have to launch a process to open a uri.
+    //
+    // Since Thunderbird does not use mitigation policies which could cause
+    // compatibility issues, we get no benefit from using
+    // ShellExecuteByExplorer.  Thus we skip it and go straight to
+    // ShellExecuteExW for Thunderbird.
+#ifndef MOZ_THUNDERBIRD
+    mozilla::LauncherVoidResult shellExecuteOk =
+        mozilla::ShellExecuteByExplorer(validatedUri.inspect(), args, verb,
+                                        workingDir, showCmd);
+    if (shellExecuteOk.isOk()) {
+      return NS_OK;
+    }
+#endif  // MOZ_THUNDERBIRD
+
+    SHELLEXECUTEINFOW sinfo = {sizeof(sinfo)};
+    sinfo.fMask = SEE_MASK_NOASYNC;
+    sinfo.lpVerb = V_BSTR(&verb);
+    sinfo.nShow = showCmd;
+    sinfo.lpFile = validatedUri.inspect();
+
+    BOOL result = ShellExecuteExW(&sinfo);
+    if (!result || reinterpret_cast<LONG_PTR>(sinfo.hInstApp) < 32) {
+      rv = NS_ERROR_FAILURE;
+    }
+  }
+
+  return rv;
+}
+
+void nsMIMEInfoWin::UpdateDefaultInfoIfStale() {
+  if (!mIsDefaultAppInfoFresh) {
+    nsCOMPtr<nsIMIMEService> mime = do_GetService("@mozilla.org/mime;1");
+    if (mime) {
+      mime->UpdateDefaultAppInfo(static_cast<nsIMIMEInfo*>(this));
+    }
+    mIsDefaultAppInfoFresh = true;
+  }
+}
+
+// Given a path to a local file, return its nsILocalHandlerApp instance.
+bool nsMIMEInfoWin::GetLocalHandlerApp(const nsAString& aCommandHandler,
+                                       nsCOMPtr<nsILocalHandlerApp>& aApp) {
+  nsCOMPtr<nsIFile> locfile;
+  nsresult rv = NS_NewLocalFile(aCommandHandler, true, getter_AddRefs(locfile));
+  if (NS_FAILED(rv)) return false;
+
+  aApp = do_CreateInstance("@mozilla.org/uriloader/local-handler-app;1");
+  if (!aApp) return false;
+
+  aApp->SetExecutable(locfile);
+  return true;
+}
+
+// Return the cleaned up file path associated with a command verb
+// located in root/Applications.
+bool nsMIMEInfoWin::GetAppsVerbCommandHandler(const nsAString& appExeName,
+                                              nsAString& applicationPath,
+                                              bool edit) {
+  nsCOMPtr<nsIWindowsRegKey> appKey =
+      do_CreateInstance("@mozilla.org/windows-registry-key;1");
+  if (!appKey) return false;
+
+  // HKEY_CLASSES_ROOT\Applications\iexplore.exe
+  nsAutoString applicationsPath;
+  applicationsPath.AppendLiteral("Applications\\");
+  applicationsPath.Append(appExeName);
+
+  nsresult rv =
+      appKey->Open(nsIWindowsRegKey::ROOT_KEY_CLASSES_ROOT, applicationsPath,
+                   nsIWindowsRegKey::ACCESS_QUERY_VALUE);
+  if (NS_FAILED(rv)) return false;
+
+  // Check for the NoOpenWith flag, if it exists
+  uint32_t value;
+  if (NS_SUCCEEDED(appKey->ReadIntValue(u"NoOpenWith"_ns, &value)) &&
+      value == 1)
+    return false;
+
+  nsAutoString dummy;
+  if (NS_SUCCEEDED(appKey->ReadStringValue(u"NoOpenWith"_ns, dummy)))
+    return false;
+
+  appKey->Close();
+
+  // HKEY_CLASSES_ROOT\Applications\iexplore.exe\shell\open\command
+  applicationsPath.AssignLiteral("Applications\\");
+  applicationsPath.Append(appExeName);
+  if (!edit)
+    applicationsPath.AppendLiteral("\\shell\\open\\command");
+  else
+    applicationsPath.AppendLiteral("\\shell\\edit\\command");
+
+  rv = appKey->Open(nsIWindowsRegKey::ROOT_KEY_CLASSES_ROOT, applicationsPath,
+                    nsIWindowsRegKey::ACCESS_QUERY_VALUE);
+  if (NS_FAILED(rv)) return false;
+
+  nsAutoString appFilesystemCommand;
+  if (NS_SUCCEEDED(appKey->ReadStringValue(u""_ns, appFilesystemCommand))) {
+    // Expand environment vars, clean up any misc.
+    if (!nsLocalFile::CleanupCmdHandlerPath(appFilesystemCommand)) return false;
+
+    applicationPath = appFilesystemCommand;
+    return true;
+  }
+  return false;
+}
+
+// Return a fully populated command string based on
+// passing information. Used in launchWithFile to trace
+// back to the full handler path based on the dll.
+// (dll, targetfile, return args, open/edit)
+bool nsMIMEInfoWin::GetDllLaunchInfo(nsIFile* aDll, nsIFile* aFile,
+                                     nsAString& args, bool edit) {
+  if (!aDll || !aFile) return false;
+
+  nsString appExeName;
+  aDll->GetLeafName(appExeName);
+
+  nsCOMPtr<nsIWindowsRegKey> appKey =
+      do_CreateInstance("@mozilla.org/windows-registry-key;1");
+  if (!appKey) return false;
+
+  // HKEY_CLASSES_ROOT\Applications\iexplore.exe
+  nsAutoString applicationsPath;
+  applicationsPath.AppendLiteral("Applications\\");
+  applicationsPath.Append(appExeName);
+
+  nsresult rv =
+      appKey->Open(nsIWindowsRegKey::ROOT_KEY_CLASSES_ROOT, applicationsPath,
+                   nsIWindowsRegKey::ACCESS_QUERY_VALUE);
+  if (NS_FAILED(rv)) return false;
+
+  // Check for the NoOpenWith flag, if it exists
+  uint32_t value;
+  rv = appKey->ReadIntValue(u"NoOpenWith"_ns, &value);
+  if (NS_SUCCEEDED(rv) && value == 1) return false;
+
+  nsAutoString dummy;
+  if (NS_SUCCEEDED(appKey->ReadStringValue(u"NoOpenWith"_ns, dummy)))
+    return false;
+
+  appKey->Close();
+
+  // HKEY_CLASSES_ROOT\Applications\iexplore.exe\shell\open\command
+  applicationsPath.AssignLiteral("Applications\\");
+  applicationsPath.Append(appExeName);
+  if (!edit)
+    applicationsPath.AppendLiteral("\\shell\\open\\command");
+  else
+    applicationsPath.AppendLiteral("\\shell\\edit\\command");
+
+  rv = appKey->Open(nsIWindowsRegKey::ROOT_KEY_CLASSES_ROOT, applicationsPath,
+                    nsIWindowsRegKey::ACCESS_QUERY_VALUE);
+  if (NS_FAILED(rv)) return false;
+
+  nsAutoString appFilesystemCommand;
+  if (NS_SUCCEEDED(appKey->ReadStringValue(u""_ns, appFilesystemCommand))) {
+    // Replace embedded environment variables.
+    uint32_t bufLength =
+        ::ExpandEnvironmentStringsW(appFilesystemCommand.get(), nullptr, 0);
+    if (bufLength == 0)  // Error
+      return false;
+
+    auto destination = mozilla::MakeUniqueFallible<wchar_t[]>(bufLength);
+    if (!destination) return false;
+    if (!::ExpandEnvironmentStringsW(appFilesystemCommand.get(),
+                                     destination.get(), bufLength))
+      return false;
+
+    appFilesystemCommand.Assign(destination.get());
+
+    // C:\Windows\System32\rundll32.exe "C:\Program Files\Windows
+    // Photo Gallery\PhotoViewer.dll", ImageView_Fullscreen %1
+    nsAutoString params;
+    constexpr auto rundllSegment = u"rundll32.exe "_ns;
+    int32_t index = appFilesystemCommand.Find(rundllSegment);
+    if (index > kNotFound) {
+      params.Append(
+          Substring(appFilesystemCommand, index + rundllSegment.Length()));
+    } else {
+      params.Append(appFilesystemCommand);
+    }
+
+    // check to make sure we have a %1 and fill it
+    constexpr auto percentOneParam = u"%1"_ns;
+    index = params.Find(percentOneParam);
+    if (index == kNotFound)  // no parameter
+      return false;
+
+    nsString target;
+    aFile->GetTarget(target);
+    params.Replace(index, 2, target);
+
+    args = params;
+
+    return true;
+  }
+  return false;
+}
+
+// Return the cleaned up file path associated with a progid command
+// verb located in root.
+bool nsMIMEInfoWin::GetProgIDVerbCommandHandler(const nsAString& appProgIDName,
+                                                nsAString& applicationPath,
+                                                bool edit) {
+  nsCOMPtr<nsIWindowsRegKey> appKey =
+      do_CreateInstance("@mozilla.org/windows-registry-key;1");
+  if (!appKey) return false;
+
+  nsAutoString appProgId(appProgIDName);
+
+  // HKEY_CLASSES_ROOT\Windows.XPSReachViewer\shell\open\command
+  if (!edit)
+    appProgId.AppendLiteral("\\shell\\open\\command");
+  else
+    appProgId.AppendLiteral("\\shell\\edit\\command");
+
+  nsresult rv = appKey->Open(nsIWindowsRegKey::ROOT_KEY_CLASSES_ROOT, appProgId,
+                             nsIWindowsRegKey::ACCESS_QUERY_VALUE);
+  if (NS_FAILED(rv)) return false;
+
+  nsAutoString appFilesystemCommand;
+  if (NS_SUCCEEDED(appKey->ReadStringValue(u""_ns, appFilesystemCommand))) {
+    // Expand environment vars, clean up any misc.
+    if (!nsLocalFile::CleanupCmdHandlerPath(appFilesystemCommand)) return false;
+
+    applicationPath = appFilesystemCommand;
+    return true;
+  }
+  return false;
+}
+
+// Helper routine used in tracking app lists. Converts path
+// entries to lower case and stores them in the trackList array.
+void nsMIMEInfoWin::ProcessPath(nsCOMPtr<nsIMutableArray>& appList,
+                                nsTArray<nsString>& trackList,
+                                const nsAString& appFilesystemCommand) {
+  nsAutoString lower(appFilesystemCommand);
+  ToLowerCase(lower);
+
+  // Don't include firefox.exe in the list
+  WCHAR exe[MAX_PATH + 1];
+  uint32_t len = GetModuleFileNameW(nullptr, exe, MAX_PATH);
+  if (len < MAX_PATH && len != 0) {
+    int32_t index = lower.Find(reinterpret_cast<const char16_t*>(exe));
+    if (index != -1) return;
+  }
+
+  nsCOMPtr<nsILocalHandlerApp> aApp;
+  if (!GetLocalHandlerApp(appFilesystemCommand, aApp)) return;
+
+  // Save in our main tracking arrays
+  appList->AppendElement(aApp);
+  trackList.AppendElement(lower);
+}
+
+// Helper routine that handles a compare between a path
+// and an array of paths.
+static bool IsPathInList(nsAString& appPath, nsTArray<nsString>& trackList) {
+  // trackList data is always lowercase, see ProcessPath
+  // above.
+  nsAutoString tmp(appPath);
+  ToLowerCase(tmp);
+
+  for (uint32_t i = 0; i < trackList.Length(); i++) {
+    if (tmp.Equals(trackList[i])) return true;
+  }
+  return false;
+}
+
+/**
+ * Returns a list of nsILocalHandlerApp objects containing local
+ * handlers associated with this mimeinfo. Implemented per
+ * platform using information in this object to generate the
+ * best list. Typically used for an "open with" style user
+ * option.
+ *
+ * @return nsIArray of nsILocalHandlerApp
+ */
+NS_IMETHODIMP
+nsMIMEInfoWin::GetPossibleLocalHandlers(nsIArray** _retval) {
+  nsresult rv;
+
+  *_retval = nullptr;
+
+  nsCOMPtr<nsIMutableArray> appList = do_CreateInstance("@mozilla.org/array;1");
+
+  if (!appList) return NS_ERROR_FAILURE;
+
+  nsTArray<nsString> trackList;
+
+  nsAutoCString fileExt;
+  GetPrimaryExtension(fileExt);
+
+  nsCOMPtr<nsIWindowsRegKey> regKey =
+      do_CreateInstance("@mozilla.org/windows-registry-key;1");
+  if (!regKey) return NS_ERROR_FAILURE;
+  nsCOMPtr<nsIWindowsRegKey> appKey =
+      do_CreateInstance("@mozilla.org/windows-registry-key;1");
+  if (!appKey) return NS_ERROR_FAILURE;
+
+  nsAutoString workingRegistryPath;
+
+  bool extKnown = false;
+  if (fileExt.IsEmpty()) {
+    extKnown = true;
+    // Mime type discovery is possible in some cases, through
+    // HKEY_CLASSES_ROOT\MIME\Database\Content Type, however, a number
+    // of file extensions related to mime type are simply not defined,
+    // (application/rss+xml & application/atom+xml are good examples)
+    // in which case we can only provide a generic list.
+    nsAutoCString mimeType;
+    GetMIMEType(mimeType);
+    if (!mimeType.IsEmpty()) {
+      workingRegistryPath.AppendLiteral("MIME\\Database\\Content Type\\");
+      workingRegistryPath.Append(NS_ConvertASCIItoUTF16(mimeType));
+
+      rv = regKey->Open(nsIWindowsRegKey::ROOT_KEY_CLASSES_ROOT,
+                        workingRegistryPath,
+                        nsIWindowsRegKey::ACCESS_QUERY_VALUE);
+      if (NS_SUCCEEDED(rv)) {
+        nsAutoString mimeFileExt;
+        if (NS_SUCCEEDED(regKey->ReadStringValue(u""_ns, mimeFileExt))) {
+          CopyUTF16toUTF8(mimeFileExt, fileExt);
+          extKnown = false;
+        }
+      }
+    }
+  }
+
+  nsAutoString fileExtToUse;
+  if (!fileExt.IsEmpty() && fileExt.First() != '.') {
+    fileExtToUse = char16_t('.');
+  }
+  fileExtToUse.Append(NS_ConvertUTF8toUTF16(fileExt));
+
+  // Note, the order in which these occur has an effect on the
+  // validity of the resulting display list.
+
+  if (!extKnown) {
+    // 1) Get the default handler if it exists
+    workingRegistryPath = fileExtToUse;
+
+    rv =
+        regKey->Open(nsIWindowsRegKey::ROOT_KEY_CLASSES_ROOT,
+                     workingRegistryPath, nsIWindowsRegKey::ACCESS_QUERY_VALUE);
+    if (NS_SUCCEEDED(rv)) {
+      nsAutoString appProgId;
+      if (NS_SUCCEEDED(regKey->ReadStringValue(u""_ns, appProgId))) {
+        // Bug 358297 - ignore the embedded internet explorer handler
+        if (appProgId != u"XPSViewer.Document"_ns) {
+          nsAutoString appFilesystemCommand;
+          if (GetProgIDVerbCommandHandler(appProgId, appFilesystemCommand,
+                                          false) &&
+              !IsPathInList(appFilesystemCommand, trackList)) {
+            ProcessPath(appList, trackList, appFilesystemCommand);
+          }
+        }
+      }
+      regKey->Close();
+    }
+
+    // 2) list HKEY_CLASSES_ROOT\.ext\OpenWithList
+
+    workingRegistryPath = fileExtToUse;
+    workingRegistryPath.AppendLiteral("\\OpenWithList");
+
+    rv =
+        regKey->Open(nsIWindowsRegKey::ROOT_KEY_CLASSES_ROOT,
+                     workingRegistryPath, nsIWindowsRegKey::ACCESS_QUERY_VALUE);
+    if (NS_SUCCEEDED(rv)) {
+      uint32_t count = 0;
+      if (NS_SUCCEEDED(regKey->GetValueCount(&count)) && count > 0) {
+        for (uint32_t index = 0; index < count; index++) {
+          nsAutoString appName;
+          if (NS_FAILED(regKey->GetValueName(index, appName))) continue;
+
+          // HKEY_CLASSES_ROOT\Applications\firefox.exe = "path params"
+          nsAutoString appFilesystemCommand;
+          if (!GetAppsVerbCommandHandler(appName, appFilesystemCommand,
+                                         false) ||
+              IsPathInList(appFilesystemCommand, trackList))
+            continue;
+          ProcessPath(appList, trackList, appFilesystemCommand);
+        }
+      }
+      regKey->Close();
+    }
+
+    // 3) List HKEY_CLASSES_ROOT\.ext\OpenWithProgids, with the
+    // different step of resolving the progids for the command handler.
+
+    workingRegistryPath = fileExtToUse;
+    workingRegistryPath.AppendLiteral("\\OpenWithProgids");
+
+    rv =
+        regKey->Open(nsIWindowsRegKey::ROOT_KEY_CLASSES_ROOT,
+                     workingRegistryPath, nsIWindowsRegKey::ACCESS_QUERY_VALUE);
+    if (NS_SUCCEEDED(rv)) {
+      uint32_t count = 0;
+      if (NS_SUCCEEDED(regKey->GetValueCount(&count)) && count > 0) {
+        for (uint32_t index = 0; index < count; index++) {
+          // HKEY_CLASSES_ROOT\.ext\OpenWithProgids\Windows.XPSReachViewer
+          nsAutoString appProgId;
+          if (NS_FAILED(regKey->GetValueName(index, appProgId))) continue;
+
+          nsAutoString appFilesystemCommand;
+          if (!GetProgIDVerbCommandHandler(appProgId, appFilesystemCommand,
+                                           false) ||
+              IsPathInList(appFilesystemCommand, trackList))
+            continue;
+          ProcessPath(appList, trackList, appFilesystemCommand);
+        }
+      }
+      regKey->Close();
+    }
+
+    // 4) Add any non configured applications located in the MRU list
+
+    // HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion
+    // \Explorer\FileExts\.ext\OpenWithList
+    workingRegistryPath = nsLiteralString(
+        u"Software\\Microsoft\\Windows\\CurrentVersion\\Explorer\\FileExts\\");
+    workingRegistryPath += fileExtToUse;
+    workingRegistryPath.AppendLiteral("\\OpenWithList");
+
+    rv =
+        regKey->Open(nsIWindowsRegKey::ROOT_KEY_CURRENT_USER,
+                     workingRegistryPath, nsIWindowsRegKey::ACCESS_QUERY_VALUE);
+    if (NS_SUCCEEDED(rv)) {
+      uint32_t count = 0;
+      if (NS_SUCCEEDED(regKey->GetValueCount(&count)) && count > 0) {
+        for (uint32_t index = 0; index < count; index++) {
+          nsAutoString appName, appValue;
+          if (NS_FAILED(regKey->GetValueName(index, appName))) continue;
+          if (appName.EqualsLiteral("MRUList")) continue;
+          if (NS_FAILED(regKey->ReadStringValue(appName, appValue))) continue;
+
+          // HKEY_CLASSES_ROOT\Applications\firefox.exe = "path params"
+          nsAutoString appFilesystemCommand;
+          if (!GetAppsVerbCommandHandler(appValue, appFilesystemCommand,
+                                         false) ||
+              IsPathInList(appFilesystemCommand, trackList))
+            continue;
+          ProcessPath(appList, trackList, appFilesystemCommand);
+        }
+      }
+    }
+
+    // 5) Add any non configured progids in the MRU list, with the
+    // different step of resolving the progids for the command handler.
+
+    // HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion
+    // \Explorer\FileExts\.ext\OpenWithProgids
+    workingRegistryPath = nsLiteralString(
+        u"Software\\Microsoft\\Windows\\CurrentVersion\\Explorer\\FileExts\\");
+    workingRegistryPath += fileExtToUse;
+    workingRegistryPath.AppendLiteral("\\OpenWithProgids");
+
+    regKey->Open(nsIWindowsRegKey::ROOT_KEY_CURRENT_USER, workingRegistryPath,
+                 nsIWindowsRegKey::ACCESS_QUERY_VALUE);
+    if (NS_SUCCEEDED(rv)) {
+      uint32_t count = 0;
+      if (NS_SUCCEEDED(regKey->GetValueCount(&count)) && count > 0) {
+        for (uint32_t index = 0; index < count; index++) {
+          nsAutoString appIndex, appProgId;
+          if (NS_FAILED(regKey->GetValueName(index, appProgId))) continue;
+
+          nsAutoString appFilesystemCommand;
+          if (!GetProgIDVerbCommandHandler(appProgId, appFilesystemCommand,
+                                           false) ||
+              IsPathInList(appFilesystemCommand, trackList))
+            continue;
+          ProcessPath(appList, trackList, appFilesystemCommand);
+        }
+      }
+      regKey->Close();
+    }
+
+    // 6) Check the perceived type value, and use this to lookup the
+    // perceivedtype open with list.
+    // http://msdn2.microsoft.com/en-us/library/aa969373.aspx
+
+    workingRegistryPath = fileExtToUse;
+
+    regKey->Open(nsIWindowsRegKey::ROOT_KEY_CLASSES_ROOT, workingRegistryPath,
+                 nsIWindowsRegKey::ACCESS_QUERY_VALUE);
+    if (NS_SUCCEEDED(rv)) {
+      nsAutoString perceivedType;
+      rv = regKey->ReadStringValue(u"PerceivedType"_ns, perceivedType);
+      if (NS_SUCCEEDED(rv)) {
+        nsAutoString openWithListPath(u"SystemFileAssociations\\"_ns);
+        openWithListPath.Append(perceivedType);  // no period
+        openWithListPath.AppendLiteral("\\OpenWithList");
+
+        nsresult rv = appKey->Open(nsIWindowsRegKey::ROOT_KEY_CLASSES_ROOT,
+                                   openWithListPath,
+                                   nsIWindowsRegKey::ACCESS_QUERY_VALUE);
+        if (NS_SUCCEEDED(rv)) {
+          uint32_t count = 0;
+          if (NS_SUCCEEDED(regKey->GetValueCount(&count)) && count > 0) {
+            for (uint32_t index = 0; index < count; index++) {
+              nsAutoString appName;
+              if (NS_FAILED(regKey->GetValueName(index, appName))) continue;
+
+              // HKEY_CLASSES_ROOT\Applications\firefox.exe = "path params"
+              nsAutoString appFilesystemCommand;
+              if (!GetAppsVerbCommandHandler(appName, appFilesystemCommand,
+                                             false) ||
+                  IsPathInList(appFilesystemCommand, trackList))
+                continue;
+              ProcessPath(appList, trackList, appFilesystemCommand);
+            }
+          }
+        }
+      }
+    }
+  }  // extKnown == false
+
+  // 7) list global HKEY_CLASSES_ROOT\*\OpenWithList
+  // Listing general purpose handlers, not specific to a mime type or file
+  // extension
+
+  workingRegistryPath = u"*\\OpenWithList"_ns;
+
+  rv = regKey->Open(nsIWindowsRegKey::ROOT_KEY_CLASSES_ROOT,
+                    workingRegistryPath, nsIWindowsRegKey::ACCESS_QUERY_VALUE);
+  if (NS_SUCCEEDED(rv)) {
+    uint32_t count = 0;
+    if (NS_SUCCEEDED(regKey->GetValueCount(&count)) && count > 0) {
+      for (uint32_t index = 0; index < count; index++) {
+        nsAutoString appName;
+        if (NS_FAILED(regKey->GetValueName(index, appName))) continue;
+
+        // HKEY_CLASSES_ROOT\Applications\firefox.exe = "path params"
+        nsAutoString appFilesystemCommand;
+        if (!GetAppsVerbCommandHandler(appName, appFilesystemCommand, false) ||
+            IsPathInList(appFilesystemCommand, trackList))
+          continue;
+        ProcessPath(appList, trackList, appFilesystemCommand);
+      }
+    }
+    regKey->Close();
+  }
+
+  // 8) General application's list - not file extension specific on windows
+  workingRegistryPath = u"Applications"_ns;
+
+  rv =
+      regKey->Open(nsIWindowsRegKey::ROOT_KEY_CLASSES_ROOT, workingRegistryPath,
+                   nsIWindowsRegKey::ACCESS_ENUMERATE_SUB_KEYS |
+                       nsIWindowsRegKey::ACCESS_QUERY_VALUE);
+  if (NS_SUCCEEDED(rv)) {
+    uint32_t count = 0;
+    if (NS_SUCCEEDED(regKey->GetChildCount(&count)) && count > 0) {
+      for (uint32_t index = 0; index < count; index++) {
+        nsAutoString appName;
+        if (NS_FAILED(regKey->GetChildName(index, appName))) continue;
+
+        // HKEY_CLASSES_ROOT\Applications\firefox.exe = "path params"
+        nsAutoString appFilesystemCommand;
+        if (!GetAppsVerbCommandHandler(appName, appFilesystemCommand, false) ||
+            IsPathInList(appFilesystemCommand, trackList))
+          continue;
+        ProcessPath(appList, trackList, appFilesystemCommand);
+      }
+    }
+  }
+
+  // Return to the caller
+  *_retval = appList;
+  NS_ADDREF(*_retval);
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsMIMEInfoWin::IsCurrentAppOSDefault(bool* _retval) {
+  *_retval = false;
+  nsCOMPtr<nsIFile> defaultApp = GetDefaultApplication();
+  if (defaultApp) {
+    // Determine if the default executable is our executable.
+    nsCOMPtr<nsIFile> ourBinary;
+    XRE_GetBinaryPath(getter_AddRefs(ourBinary));
+    bool isSame = false;
+    nsresult rv = defaultApp->Equals(ourBinary, &isSame);
+    if (NS_FAILED(rv)) {
+      return rv;
+    }
+    *_retval = isSame;
+  }
+  return NS_OK;
+}
diff --git a/uriloader/exthandler/win/nsMIMEInfoWin.h b/uriloader/exthandler/win/nsMIMEInfoWin.h
new file mode 100644
index 0000000000..fa972b23a9
--- /dev/null
+++ b/uriloader/exthandler/win/nsMIMEInfoWin.h
@@ -0,0 +1,79 @@
+/* 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 nsMIMEInfoWin_h_
+#define nsMIMEInfoWin_h_
+
+#include "nsMIMEInfoImpl.h"
+#include "nsIPropertyBag.h"
+#include "nsIMutableArray.h"
+#include "nsTArray.h"
+
+class nsMIMEInfoWin : public nsMIMEInfoBase, public nsIPropertyBag {
+  virtual ~nsMIMEInfoWin();
+
+ public:
+  explicit nsMIMEInfoWin(const char* aType = "") : nsMIMEInfoBase(aType) {}
+  explicit nsMIMEInfoWin(const nsACString& aMIMEType)
+      : nsMIMEInfoBase(aMIMEType) {}
+  nsMIMEInfoWin(const nsACString& aType, HandlerClass aClass)
+      : nsMIMEInfoBase(aType, aClass) {}
+
+  NS_IMETHOD LaunchWithFile(nsIFile* aFile) override;
+  NS_IMETHOD GetHasDefaultHandler(bool* _retval) override;
+  NS_IMETHOD GetPossibleLocalHandlers(nsIArray** _retval) override;
+  NS_IMETHOD IsCurrentAppOSDefault(bool* _retval) override;
+
+  void UpdateDefaultInfoIfStale();
+
+  NS_DECL_ISUPPORTS_INHERITED
+  NS_DECL_NSIPROPERTYBAG
+
+  void SetDefaultApplicationHandler(nsIFile* aDefaultApplication) {
+    mDefaultApplication = aDefaultApplication;
+  }
+
+ protected:
+  nsIFile* GetDefaultApplication() {
+    UpdateDefaultInfoIfStale();
+    return mDefaultApplication;
+  }
+
+  virtual nsresult LoadUriInternal(nsIURI* aURI);
+  virtual nsresult LaunchDefaultWithFile(nsIFile* aFile);
+
+ private:
+  nsCOMPtr<nsIFile> mDefaultApplication;
+
+  // Given a path to a local handler, return its
+  // nsILocalHandlerApp instance.
+  bool GetLocalHandlerApp(const nsAString& aCommandHandler,
+                          nsCOMPtr<nsILocalHandlerApp>& aApp);
+
+  // Return the cleaned up file path associated
+  // with a command verb located in root/Applications.
+  bool GetAppsVerbCommandHandler(const nsAString& appExeName,
+                                 nsAString& applicationPath, bool bEdit);
+
+  // Return the cleaned up file path associated
+  // with a progid command verb located in root.
+  bool GetProgIDVerbCommandHandler(const nsAString& appProgIDName,
+                                   nsAString& applicationPath, bool bEdit);
+
+  // Lookup a rundll command handler and return
+  // a populated command template for use with rundll32.exe.
+  bool GetDllLaunchInfo(nsIFile* aDll, nsIFile* aFile, nsAString& args,
+                        bool bEdit);
+
+  // Helper routine used in tracking app lists
+  void ProcessPath(nsCOMPtr<nsIMutableArray>& appList,
+                   nsTArray<nsString>& trackList,
+                   const nsAString& appFilesystemCommand);
+
+  // Helper routine to call mozilla::ShellExecuteByExplorer
+  nsresult ShellExecuteWithIFile(nsIFile* aExecutable, int aArgc,
+                                 const wchar_t** aArgv);
+};
+
+#endif
diff --git a/uriloader/exthandler/win/nsOSHelperAppService.cpp b/uriloader/exthandler/win/nsOSHelperAppService.cpp
new file mode 100644
index 0000000000..e3a2ae9873
--- /dev/null
+++ b/uriloader/exthandler/win/nsOSHelperAppService.cpp
@@ -0,0 +1,609 @@
+/* -*- Mode: C++; tab-width: 3; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim:set ts=2 sts=2 sw=2 et cin:
+ *
+ * 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/. */
+
+#include "nsComponentManagerUtils.h"
+#include "nsOSHelperAppService.h"
+#include "nsISupports.h"
+#include "nsString.h"
+#include "nsIMIMEInfo.h"
+#include "nsMIMEInfoWin.h"
+#include "nsMimeTypes.h"
+#include "nsNativeCharsetUtils.h"
+#include "nsLocalFile.h"
+#include "nsIWindowsRegKey.h"
+#include "nsXULAppAPI.h"
+#include "mozilla/UniquePtrExtensions.h"
+
+// shellapi.h is needed to build with WIN32_LEAN_AND_MEAN
+#include <shellapi.h>
+#include <shlwapi.h>
+
+#define LOG(...) MOZ_LOG(sLog, mozilla::LogLevel::Debug, (__VA_ARGS__))
+
+// helper methods: forward declarations...
+static nsresult GetExtensionFromWindowsMimeDatabase(const nsACString& aMimeType,
+                                                    nsString& aFileExtension);
+
+nsOSHelperAppService::nsOSHelperAppService()
+    : nsExternalHelperAppService(), mAppAssoc(nullptr) {
+  CoInitialize(nullptr);
+  CoCreateInstance(CLSID_ApplicationAssociationRegistration, nullptr,
+                   CLSCTX_INPROC, IID_IApplicationAssociationRegistration,
+                   (void**)&mAppAssoc);
+}
+
+nsOSHelperAppService::~nsOSHelperAppService() {
+  if (mAppAssoc) mAppAssoc->Release();
+  mAppAssoc = nullptr;
+  CoUninitialize();
+}
+
+// The windows registry provides a mime database key which lists a set of mime
+// types and corresponding "Extension" values. we can use this to look up our
+// mime type to see if there is a preferred extension for the mime type.
+static nsresult GetExtensionFromWindowsMimeDatabase(const nsACString& aMimeType,
+                                                    nsString& aFileExtension) {
+  nsAutoString mimeDatabaseKey;
+  mimeDatabaseKey.AssignLiteral("MIME\\Database\\Content Type\\");
+
+  AppendASCIItoUTF16(aMimeType, mimeDatabaseKey);
+
+  nsCOMPtr<nsIWindowsRegKey> regKey =
+      do_CreateInstance("@mozilla.org/windows-registry-key;1");
+  if (!regKey) return NS_ERROR_NOT_AVAILABLE;
+
+  nsresult rv =
+      regKey->Open(nsIWindowsRegKey::ROOT_KEY_CLASSES_ROOT, mimeDatabaseKey,
+                   nsIWindowsRegKey::ACCESS_QUERY_VALUE);
+
+  if (NS_SUCCEEDED(rv))
+    regKey->ReadStringValue(u"Extension"_ns, aFileExtension);
+
+  return NS_OK;
+}
+
+nsresult nsOSHelperAppService::OSProtocolHandlerExists(
+    const char* aProtocolScheme, bool* aHandlerExists) {
+  // look up the protocol scheme in the windows registry....if we find a match
+  // then we have a handler for it...
+  *aHandlerExists = false;
+  if (aProtocolScheme && *aProtocolScheme) {
+    NS_ENSURE_TRUE(mAppAssoc, NS_ERROR_NOT_AVAILABLE);
+    wchar_t* pResult = nullptr;
+    NS_ConvertASCIItoUTF16 scheme(aProtocolScheme);
+    // We are responsible for freeing returned strings.
+    HRESULT hr = mAppAssoc->QueryCurrentDefault(scheme.get(), AT_URLPROTOCOL,
+                                                AL_EFFECTIVE, &pResult);
+    if (SUCCEEDED(hr)) {
+      CoTaskMemFree(pResult);
+      nsCOMPtr<nsIWindowsRegKey> regKey =
+          do_CreateInstance("@mozilla.org/windows-registry-key;1");
+      if (!regKey) {
+        return NS_ERROR_NOT_AVAILABLE;
+      }
+
+      nsresult rv = regKey->Open(nsIWindowsRegKey::ROOT_KEY_CLASSES_ROOT,
+                                 nsDependentString(scheme.get()),
+                                 nsIWindowsRegKey::ACCESS_QUERY_VALUE);
+      if (NS_FAILED(rv)) {
+        // Open will fail if the registry key path doesn't exist.
+        return NS_OK;
+      }
+
+      bool hasValue;
+      rv = regKey->HasValue(u"URL Protocol"_ns, &hasValue);
+      if (NS_FAILED(rv)) {
+        return NS_ERROR_FAILURE;
+      }
+      if (!hasValue) {
+        return NS_OK;
+      }
+
+      *aHandlerExists = true;
+    }
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP nsOSHelperAppService::GetApplicationDescription(
+    const nsACString& aScheme, nsAString& _retval) {
+  nsCOMPtr<nsIWindowsRegKey> regKey =
+      do_CreateInstance("@mozilla.org/windows-registry-key;1");
+  if (!regKey) return NS_ERROR_NOT_AVAILABLE;
+
+  NS_ConvertASCIItoUTF16 buf(aScheme);
+
+  wchar_t result[1024];
+  DWORD resultSize = 1024;
+  HRESULT hr = AssocQueryString(0x1000 /* ASSOCF_IS_PROTOCOL */,
+                                ASSOCSTR_FRIENDLYAPPNAME, buf.get(), NULL,
+                                result, &resultSize);
+  if (SUCCEEDED(hr)) {
+    _retval = result;
+    return NS_OK;
+  }
+
+  NS_ENSURE_TRUE(mAppAssoc, NS_ERROR_NOT_AVAILABLE);
+  wchar_t* pResult = nullptr;
+  // We are responsible for freeing returned strings.
+  hr = mAppAssoc->QueryCurrentDefault(buf.get(), AT_URLPROTOCOL, AL_EFFECTIVE,
+                                      &pResult);
+  if (SUCCEEDED(hr)) {
+    nsCOMPtr<nsIFile> app;
+    nsAutoString appInfo(pResult);
+    CoTaskMemFree(pResult);
+    if (NS_SUCCEEDED(GetDefaultAppInfo(appInfo, _retval, getter_AddRefs(app))))
+      return NS_OK;
+  }
+  return NS_ERROR_NOT_AVAILABLE;
+}
+
+NS_IMETHODIMP nsOSHelperAppService::IsCurrentAppOSDefaultForProtocol(
+    const nsACString& aScheme, bool* _retval) {
+  *_retval = false;
+
+  NS_ENSURE_TRUE(mAppAssoc, NS_ERROR_NOT_AVAILABLE);
+
+  NS_ConvertASCIItoUTF16 buf(aScheme);
+
+  // Find the progID
+  wchar_t* pResult = nullptr;
+  HRESULT hr = mAppAssoc->QueryCurrentDefault(buf.get(), AT_URLPROTOCOL,
+                                              AL_EFFECTIVE, &pResult);
+  if (FAILED(hr)) {
+    return NS_ERROR_FAILURE;
+  }
+  nsAutoString progID(pResult);
+  // We are responsible for freeing returned strings.
+  CoTaskMemFree(pResult);
+
+  // Find the default executable.
+  nsAutoString description;
+  nsCOMPtr<nsIFile> appFile;
+  nsresult rv = GetDefaultAppInfo(progID, description, getter_AddRefs(appFile));
+  if (NS_FAILED(rv)) {
+    return rv;
+  }
+  // Determine if the default executable is our executable.
+  nsCOMPtr<nsIFile> ourBinary;
+  XRE_GetBinaryPath(getter_AddRefs(ourBinary));
+  bool isSame = false;
+  rv = appFile->Equals(ourBinary, &isSame);
+  if (NS_FAILED(rv)) {
+    return rv;
+  }
+  *_retval = isSame;
+  return NS_OK;
+}
+
+// GetMIMEInfoFromRegistry: This function obtains the values of some of the
+// nsIMIMEInfo attributes for the mimeType/extension associated with the input
+// registry key.  The default entry for that key is the name of a registry key
+// under HKEY_CLASSES_ROOT.  The default value for *that* key is the descriptive
+// name of the type.  The EditFlags value is a binary value; the low order bit
+// of the third byte of which indicates that the user does not need to be
+// prompted.
+//
+// This function sets only the Description attribute of the input nsIMIMEInfo.
+/* static */
+nsresult nsOSHelperAppService::GetMIMEInfoFromRegistry(const nsString& fileType,
+                                                       nsIMIMEInfo* pInfo) {
+  nsresult rv = NS_OK;
+
+  NS_ENSURE_ARG(pInfo);
+  nsCOMPtr<nsIWindowsRegKey> regKey =
+      do_CreateInstance("@mozilla.org/windows-registry-key;1");
+  if (!regKey) return NS_ERROR_NOT_AVAILABLE;
+
+  rv = regKey->Open(nsIWindowsRegKey::ROOT_KEY_CLASSES_ROOT, fileType,
+                    nsIWindowsRegKey::ACCESS_QUERY_VALUE);
+  if (NS_FAILED(rv)) return NS_ERROR_FAILURE;
+
+  // OK, the default value here is the description of the type.
+  nsAutoString description;
+  rv = regKey->ReadStringValue(u""_ns, description);
+  if (NS_SUCCEEDED(rv)) pInfo->SetDescription(description);
+
+  return NS_OK;
+}
+
+/////////////////////////////////////////////////////////////////////////////////////////////////
+// method overrides used to gather information from the windows registry for
+// various mime types.
+////////////////////////////////////////////////////////////////////////////////////////////////
+
+/// Looks up the type for the extension aExt and compares it to aType
+/* static */
+bool nsOSHelperAppService::typeFromExtEquals(const char16_t* aExt,
+                                             const char* aType) {
+  if (!aType) return false;
+  nsAutoString fileExtToUse;
+  if (aExt[0] != char16_t('.')) fileExtToUse = char16_t('.');
+
+  fileExtToUse.Append(aExt);
+
+  bool eq = false;
+  nsCOMPtr<nsIWindowsRegKey> regKey =
+      do_CreateInstance("@mozilla.org/windows-registry-key;1");
+  if (!regKey) return eq;
+
+  nsresult rv =
+      regKey->Open(nsIWindowsRegKey::ROOT_KEY_CLASSES_ROOT, fileExtToUse,
+                   nsIWindowsRegKey::ACCESS_QUERY_VALUE);
+  if (NS_FAILED(rv)) return eq;
+
+  nsAutoString type;
+  rv = regKey->ReadStringValue(u"Content Type"_ns, type);
+  if (NS_SUCCEEDED(rv)) eq = type.LowerCaseEqualsASCII(aType);
+
+  return eq;
+}
+
+// The "real" name of a given helper app (as specified by the path to the
+// executable file held in various registry keys) is stored n the VERSIONINFO
+// block in the file's resources. We need to find the path to the executable
+// and then retrieve the "FileDescription" field value from the file.
+nsresult nsOSHelperAppService::GetDefaultAppInfo(
+    const nsAString& aAppInfo, nsAString& aDefaultDescription,
+    nsIFile** aDefaultApplication) {
+  nsAutoString handlerCommand;
+
+  // If all else fails, use the file type key name, which will be
+  // something like "pngfile" for .pngs, "WMVFile" for .wmvs, etc.
+  aDefaultDescription = aAppInfo;
+  *aDefaultApplication = nullptr;
+
+  if (aAppInfo.IsEmpty()) return NS_ERROR_FAILURE;
+
+  // aAppInfo may be a file, file path, program id, or
+  // Applications reference -
+  // c:\dir\app.exe
+  // Applications\appfile.exe/dll (shell\open...)
+  // ProgID.progid (shell\open...)
+
+  nsAutoString handlerKeyName(aAppInfo);
+
+  nsCOMPtr<nsIWindowsRegKey> chkKey =
+      do_CreateInstance("@mozilla.org/windows-registry-key;1");
+  if (!chkKey) return NS_ERROR_FAILURE;
+
+  nsresult rv =
+      chkKey->Open(nsIWindowsRegKey::ROOT_KEY_CLASSES_ROOT, handlerKeyName,
+                   nsIWindowsRegKey::ACCESS_QUERY_VALUE);
+  if (NS_FAILED(rv)) {
+    // It's a file system path to a handler
+    handlerCommand.Assign(aAppInfo);
+  } else {
+    handlerKeyName.AppendLiteral("\\shell\\open\\command");
+    nsCOMPtr<nsIWindowsRegKey> regKey =
+        do_CreateInstance("@mozilla.org/windows-registry-key;1");
+    if (!regKey) return NS_ERROR_FAILURE;
+
+    nsresult rv =
+        regKey->Open(nsIWindowsRegKey::ROOT_KEY_CLASSES_ROOT, handlerKeyName,
+                     nsIWindowsRegKey::ACCESS_QUERY_VALUE);
+    if (NS_FAILED(rv)) return NS_ERROR_FAILURE;
+
+    // OK, the default value here is the description of the type.
+    rv = regKey->ReadStringValue(u""_ns, handlerCommand);
+    if (NS_FAILED(rv)) {
+      // Check if there is a DelegateExecute string
+      nsAutoString delegateExecute;
+      rv = regKey->ReadStringValue(u"DelegateExecute"_ns, delegateExecute);
+      NS_ENSURE_SUCCESS(rv, rv);
+
+      // Look for InProcServer32
+      nsAutoString delegateExecuteRegPath;
+      delegateExecuteRegPath.AssignLiteral("CLSID\\");
+      delegateExecuteRegPath.Append(delegateExecute);
+      delegateExecuteRegPath.AppendLiteral("\\InProcServer32");
+      rv = chkKey->Open(nsIWindowsRegKey::ROOT_KEY_CLASSES_ROOT,
+                        delegateExecuteRegPath,
+                        nsIWindowsRegKey::ACCESS_QUERY_VALUE);
+      if (NS_SUCCEEDED(rv)) {
+        rv = chkKey->ReadStringValue(u""_ns, handlerCommand);
+      }
+
+      if (NS_FAILED(rv)) {
+        // Look for LocalServer32
+        delegateExecuteRegPath.AssignLiteral("CLSID\\");
+        delegateExecuteRegPath.Append(delegateExecute);
+        delegateExecuteRegPath.AppendLiteral("\\LocalServer32");
+        rv = chkKey->Open(nsIWindowsRegKey::ROOT_KEY_CLASSES_ROOT,
+                          delegateExecuteRegPath,
+                          nsIWindowsRegKey::ACCESS_QUERY_VALUE);
+        NS_ENSURE_SUCCESS(rv, rv);
+        rv = chkKey->ReadStringValue(u""_ns, handlerCommand);
+        NS_ENSURE_SUCCESS(rv, rv);
+      }
+    }
+  }
+
+  // XXX FIXME: If this fails, the UI will display the full command
+  // string.
+  // There are some rare cases this can happen - ["url.dll" -foo]
+  // for example won't resolve correctly to the system dir. The
+  // subsequent launch of the helper app will work though.
+  nsCOMPtr<nsILocalFileWin> lf = new nsLocalFile();
+  rv = lf->InitWithCommandLine(handlerCommand);
+  NS_ENSURE_SUCCESS(rv, rv);
+  lf.forget(aDefaultApplication);
+
+  wchar_t friendlyName[1024];
+  DWORD friendlyNameSize = 1024;
+  HRESULT hr = AssocQueryString(ASSOCF_NONE, ASSOCSTR_FRIENDLYAPPNAME,
+                                PromiseFlatString(aAppInfo).get(), NULL,
+                                friendlyName, &friendlyNameSize);
+  if (SUCCEEDED(hr) && friendlyNameSize > 1) {
+    aDefaultDescription.Assign(friendlyName, friendlyNameSize - 1);
+  }
+
+  return NS_OK;
+}
+
+already_AddRefed<nsMIMEInfoWin> nsOSHelperAppService::GetByExtension(
+    const nsString& aFileExt, const char* aTypeHint) {
+  if (aFileExt.IsEmpty()) return nullptr;
+
+  // Determine the mime type.
+  nsAutoCString typeToUse;
+  if (aTypeHint && *aTypeHint) {
+    typeToUse.Assign(aTypeHint);
+  } else if (!GetMIMETypeFromOSForExtension(NS_ConvertUTF16toUTF8(aFileExt),
+                                            typeToUse)) {
+    return nullptr;
+  }
+
+  RefPtr<nsMIMEInfoWin> mimeInfo = new nsMIMEInfoWin(typeToUse);
+
+  // Our extension APIs expect extensions without the '.', so normalize:
+  uint32_t dotlessIndex = aFileExt.First() != char16_t('.') ? 0 : 1;
+  nsAutoCString lowerFileExt =
+      NS_ConvertUTF16toUTF8(Substring(aFileExt, dotlessIndex));
+  ToLowerCase(lowerFileExt);
+  mimeInfo->AppendExtension(lowerFileExt);
+  mimeInfo->SetPreferredAction(nsIMIMEInfo::saveToDisk);
+
+  if (NS_FAILED(InternalSetDefaultsOnMIME(mimeInfo))) {
+    return nullptr;
+  }
+
+  return mimeInfo.forget();
+}
+
+nsresult nsOSHelperAppService::InternalSetDefaultsOnMIME(
+    nsMIMEInfoWin* aMIMEInfo) {
+  NS_ENSURE_ARG(aMIMEInfo);
+
+  nsAutoCString primaryExt;
+  aMIMEInfo->GetPrimaryExtension(primaryExt);
+
+  if (primaryExt.IsEmpty()) {
+    return NS_ERROR_FAILURE;
+  }
+
+  // windows registry assumes your file extension is going to include the '.',
+  // but our APIs don't have it, so add it:
+  nsAutoString assocType = NS_ConvertUTF8toUTF16(primaryExt);
+  if (assocType.First() != char16_t('.')) {
+    assocType.Insert(char16_t('.'), 0);
+  }
+
+  nsAutoString appInfo;
+  bool found;
+
+  // Retrieve the default application for this extension
+  NS_ENSURE_TRUE(mAppAssoc, NS_ERROR_NOT_AVAILABLE);
+  wchar_t* pResult = nullptr;
+  HRESULT hr = mAppAssoc->QueryCurrentDefault(assocType.get(), AT_FILEEXTENSION,
+                                              AL_EFFECTIVE, &pResult);
+  if (SUCCEEDED(hr)) {
+    found = true;
+    appInfo.Assign(pResult);
+    CoTaskMemFree(pResult);
+  } else {
+    found = false;
+  }
+
+  // Bug 358297 - ignore the default handler, force the user to choose app
+  if (appInfo.EqualsLiteral("XPSViewer.Document")) found = false;
+
+  if (!found) {
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+
+  // Get other nsIMIMEInfo fields from registry, if possible.
+  nsAutoString defaultDescription;
+  nsCOMPtr<nsIFile> defaultApplication;
+
+  if (NS_FAILED(GetDefaultAppInfo(appInfo, defaultDescription,
+                                  getter_AddRefs(defaultApplication)))) {
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+
+  aMIMEInfo->SetDefaultDescription(defaultDescription);
+  aMIMEInfo->SetDefaultApplicationHandler(defaultApplication);
+
+  // Grab the general description
+  GetMIMEInfoFromRegistry(appInfo, aMIMEInfo);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsOSHelperAppService::GetMIMEInfoFromOS(const nsACString& aMIMEType,
+                                        const nsACString& aFileExt,
+                                        bool* aFound, nsIMIMEInfo** aMIMEInfo) {
+  *aFound = false;
+
+  const nsCString& flatType = PromiseFlatCString(aMIMEType);
+  nsAutoString fileExtension;
+  CopyUTF8toUTF16(aFileExt, fileExtension);
+
+  /* XXX The octet-stream check is a gross hack to wallpaper over the most
+   * common Win32 extension issues caused by the fix for bug 116938.  See bug
+   * 120327, comment 271 for why this is needed.  Not even sure we
+   * want to remove this once we have fixed all this stuff to work
+   * right; any info we get from the OS on this type is pretty much
+   * useless....
+   */
+  bool haveMeaningfulMimeType =
+      !aMIMEType.IsEmpty() &&
+      !aMIMEType.LowerCaseEqualsLiteral(APPLICATION_OCTET_STREAM);
+  LOG("Extension lookup on '%S' with mimetype '%s'%s\n",
+      static_cast<const wchar_t*>(fileExtension.get()), flatType.get(),
+      haveMeaningfulMimeType ? " (treated as meaningful)" : "");
+
+  RefPtr<nsMIMEInfoWin> mi;
+
+  // We should have *something* to go on here.
+  nsAutoString extensionFromMimeType;
+  if (haveMeaningfulMimeType) {
+    GetExtensionFromWindowsMimeDatabase(aMIMEType, extensionFromMimeType);
+  }
+  if (fileExtension.IsEmpty() && extensionFromMimeType.IsEmpty()) {
+    // Without an extension from the mimetype or the file, we can't
+    // do anything here.
+    mi = new nsMIMEInfoWin(flatType.get());
+    mi.forget(aMIMEInfo);
+    return NS_OK;
+  }
+
+  // Either fileExtension or extensionFromMimeType must now be non-empty.
+
+  *aFound = true;
+
+  // On Windows, we prefer the file extension for lookups over the mimetype,
+  // because that's how windows does things.
+  // If we have no file extension or it doesn't match the mimetype, use the
+  // mime type's default file extension instead.
+  bool usedMimeTypeExtensionForLookup = false;
+  if (fileExtension.IsEmpty() ||
+      (!extensionFromMimeType.IsEmpty() &&
+       !typeFromExtEquals(fileExtension.get(), flatType.get()))) {
+    usedMimeTypeExtensionForLookup = true;
+    fileExtension = extensionFromMimeType;
+    LOG("Now using '%s' mimetype's default file extension '%S' for lookup\n",
+        flatType.get(), static_cast<const wchar_t*>(fileExtension.get()));
+  }
+
+  // If we have an extension, use it for lookup:
+  mi = GetByExtension(fileExtension, flatType.get());
+  LOG("Extension lookup on '%S' found: 0x%p\n",
+      static_cast<const wchar_t*>(fileExtension.get()), mi.get());
+
+  if (mi) {
+    bool hasDefault = false;
+    mi->GetHasDefaultHandler(&hasDefault);
+    // If we don't find a default handler description, see if we can find one
+    // using the mimetype.
+    if (!hasDefault && !usedMimeTypeExtensionForLookup) {
+      RefPtr<nsMIMEInfoWin> miFromMimeType =
+          GetByExtension(extensionFromMimeType, flatType.get());
+      LOG("Mime-based ext. lookup for '%S' found 0x%p\n",
+          static_cast<const wchar_t*>(extensionFromMimeType.get()),
+          miFromMimeType.get());
+      if (miFromMimeType) {
+        nsAutoString desc;
+        miFromMimeType->GetDefaultDescription(desc);
+        mi->SetDefaultDescription(desc);
+      }
+    }
+    mi.forget(aMIMEInfo);
+    return NS_OK;
+  }
+
+  // The extension didn't work. Try the extension from the mimetype if
+  // different:
+  if (!extensionFromMimeType.IsEmpty() && !usedMimeTypeExtensionForLookup) {
+    mi = GetByExtension(extensionFromMimeType, flatType.get());
+    LOG("Mime-based ext. lookup for '%S' found 0x%p\n",
+        static_cast<const wchar_t*>(extensionFromMimeType.get()), mi.get());
+  }
+  if (mi) {
+    mi.forget(aMIMEInfo);
+    return NS_OK;
+  }
+  // This didn't work either, so just return an empty dummy mimeinfo.
+  *aFound = false;
+  mi = new nsMIMEInfoWin(flatType.get());
+  // If we didn't resort to the mime type's extension, we must have had a
+  // valid extension, so stick its lowercase version on the mime info.
+  if (!usedMimeTypeExtensionForLookup) {
+    nsAutoCString lowerFileExt;
+    ToLowerCase(aFileExt, lowerFileExt);
+    mi->AppendExtension(lowerFileExt);
+  }
+  mi.forget(aMIMEInfo);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsOSHelperAppService::UpdateDefaultAppInfo(nsIMIMEInfo* aMIMEInfo) {
+  InternalSetDefaultsOnMIME(static_cast<nsMIMEInfoWin*>(aMIMEInfo));
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsOSHelperAppService::GetProtocolHandlerInfoFromOS(const nsACString& aScheme,
+                                                   bool* found,
+                                                   nsIHandlerInfo** _retval) {
+  NS_ASSERTION(!aScheme.IsEmpty(), "No scheme was specified!");
+
+  nsresult rv =
+      OSProtocolHandlerExists(nsPromiseFlatCString(aScheme).get(), found);
+  if (NS_FAILED(rv)) return rv;
+
+  nsMIMEInfoWin* handlerInfo =
+      new nsMIMEInfoWin(aScheme, nsMIMEInfoBase::eProtocolInfo);
+  NS_ENSURE_TRUE(handlerInfo, NS_ERROR_OUT_OF_MEMORY);
+  NS_ADDREF(*_retval = handlerInfo);
+
+  if (!*found) {
+    // Code that calls this requires an object regardless if the OS has
+    // something for us, so we return the empty object.
+    return NS_OK;
+  }
+
+  nsAutoString desc;
+  GetApplicationDescription(aScheme, desc);
+  handlerInfo->SetDefaultDescription(desc);
+
+  return NS_OK;
+}
+
+bool nsOSHelperAppService::GetMIMETypeFromOSForExtension(
+    const nsACString& aExtension, nsACString& aMIMEType) {
+  if (aExtension.IsEmpty()) return false;
+
+  // windows registry assumes your file extension is going to include the '.'.
+  // so make sure it's there...
+  nsAutoString fileExtToUse;
+  if (aExtension.First() != '.') fileExtToUse = char16_t('.');
+
+  AppendUTF8toUTF16(aExtension, fileExtToUse);
+
+  // Try to get an entry from the windows registry.
+  nsCOMPtr<nsIWindowsRegKey> regKey =
+      do_CreateInstance("@mozilla.org/windows-registry-key;1");
+  if (!regKey) return false;
+
+  nsresult rv =
+      regKey->Open(nsIWindowsRegKey::ROOT_KEY_CLASSES_ROOT, fileExtToUse,
+                   nsIWindowsRegKey::ACCESS_QUERY_VALUE);
+  if (NS_FAILED(rv)) return false;
+
+  nsAutoString mimeType;
+  if (NS_FAILED(regKey->ReadStringValue(u"Content Type"_ns, mimeType)) ||
+      mimeType.IsEmpty()) {
+    return false;
+  }
+  // Content-Type is always in ASCII
+  aMIMEType.Truncate();
+  LossyAppendUTF16toASCII(mimeType, aMIMEType);
+  return true;
+}
diff --git a/uriloader/exthandler/win/nsOSHelperAppService.h b/uriloader/exthandler/win/nsOSHelperAppService.h
new file mode 100644
index 0000000000..ff7c597217
--- /dev/null
+++ b/uriloader/exthandler/win/nsOSHelperAppService.h
@@ -0,0 +1,76 @@
+/* -*- Mode: C++; tab-width: 3; 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 nsOSHelperAppService_h__
+#define nsOSHelperAppService_h__
+
+// The OS helper app service is a subclass of nsExternalHelperAppService and is
+// implemented on each platform. It contains platform specific code for finding
+// helper applications for a given mime type in addition to launching those
+// applications.
+
+#include "nsExternalHelperAppService.h"
+#include "nsCExternalHandlerService.h"
+#include "nsCOMPtr.h"
+#include <windows.h>
+#include <shlobj.h>
+
+class nsMIMEInfoWin;
+class nsIMIMEInfo;
+
+class nsOSHelperAppService : public nsExternalHelperAppService {
+ public:
+  nsOSHelperAppService();
+  virtual ~nsOSHelperAppService();
+
+  // override nsIExternalProtocolService methods
+  NS_IMETHOD OSProtocolHandlerExists(const char* aProtocolScheme,
+                                     bool* aHandlerExists) override;
+  nsresult LoadUriInternal(nsIURI* aURL);
+  NS_IMETHOD GetApplicationDescription(const nsACString& aScheme,
+                                       nsAString& _retval) override;
+
+  NS_IMETHOD IsCurrentAppOSDefaultForProtocol(const nsACString& aScheme,
+                                              bool* _retval) override;
+
+  // method overrides for windows registry look up steps....
+  NS_IMETHOD GetMIMEInfoFromOS(const nsACString& aMIMEType,
+                               const nsACString& aFileExt, bool* aFound,
+                               nsIMIMEInfo** aMIMEInfo) override;
+  NS_IMETHOD UpdateDefaultAppInfo(nsIMIMEInfo* aMIMEInfo) override;
+  NS_IMETHOD GetProtocolHandlerInfoFromOS(const nsACString& aScheme,
+                                          bool* found,
+                                          nsIHandlerInfo** _retval);
+  virtual bool GetMIMETypeFromOSForExtension(const nsACString& aExtension,
+                                             nsACString& aMIMEType) override;
+
+  /** Get the string value of a registry value and store it in result.
+   * @return true on success, false on failure
+   */
+  static bool GetValueString(HKEY hKey, const char16_t* pValueName,
+                             nsAString& result);
+
+ protected:
+  nsresult GetDefaultAppInfo(const nsAString& aTypeName,
+                             nsAString& aDefaultDescription,
+                             nsIFile** aDefaultApplication);
+  // Lookup a mime info by extension, using an optional type hint
+  already_AddRefed<nsMIMEInfoWin> GetByExtension(
+      const nsString& aFileExt, const char* aTypeHint = nullptr);
+  nsresult InternalSetDefaultsOnMIME(nsMIMEInfoWin* aMIMEInfo);
+  nsresult FindOSMimeInfoForType(const char* aMimeContentType, nsIURI* aURI,
+                                 char** aFileExtension,
+                                 nsIMIMEInfo** aMIMEInfo);
+
+  static nsresult GetMIMEInfoFromRegistry(const nsString& fileType,
+                                          nsIMIMEInfo* pInfo);
+  /// Looks up the type for the extension aExt and compares it to aType
+  static bool typeFromExtEquals(const char16_t* aExt, const char* aType);
+
+ private:
+  IApplicationAssociationRegistration* mAppAssoc;
+};
+
+#endif  // nsOSHelperAppService_h__