Bug 1570845 - Call CoAllowSetForegroundWindow before ShellExecute to launch an application in the foreground. r=aklotz

Differential Revision: https://phabricator.services.mozilla.com/D43536

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

widget/windows/ShellHeaderOnlyUtils.h

@@ -126,6 +126,12 @@ inline LauncherVoidResult ShellExecuteByExplorer(const _bstr_t& aPath,
     return LAUNCHER_ERROR_FROM_HRESULT(hr);
   }
 
+  // Passing the foreground privilege so that the shell can launch an
+  // application in the foreground.  If CoAllowSetForegroundWindow fails,
+  // we continue because it's not fatal.
+  hr = ::CoAllowSetForegroundWindow(shellDisp, nullptr);
+  MOZ_ASSERT(SUCCEEDED(hr));
+
   // shellapi.h macros interfere with the correct naming of the method being
   // called on IShellDispatch2. Temporarily remove that definition.
 #if defined(ShellExecute)