[BUG]: QCefDownloadItem::start() path problem

[L-Super]

Describe the bug 【Bug描述】

https://github.com/CefView/QCefView/blob/6d42213de75d528916f8b39d97ff711db7bd0586/example/QCefViewTest/DownloadManager.cpp#L25

当我在用QCefViewTest测试QCefDownloadItem 的下载功能时，发现调用start()的时候，如果传入的路径为D:/CppProject/QCefView右斜杠形式时，则会下载失败。改为双斜杠D:\\CppProject\\QCefView形式即可正常下载。

右斜杠形式控制台输出如下：

+++ "CCefClientDelegate::onDownloadUpdated"
--- "CCefClientDelegate::onDownloadUpdated"
+++ "CCefClientDelegate::onBeforeDownload"
onNewDownloadItem suggest name "qtcharts-everywhere-opensource-src-5.15.9.tar.xz"
DownloadManager::AddNewDownloadItem:   id:  1 
   name:  ""
   path:  ""
   percent:  0 %,  4253692 / 0
   canceled:  false
   complete:  false
--- "CCefClientDelegate::onBeforeDownload"
+++ "CCefClientDelegate::onDownloadUpdated"
DownloadManager::UpdateDownloadItem:   id:  1
   name:  ""
   path:  ""
   percent:  0 %,  4253692 / 0
   canceled:  false
   complete:  false
--- "CCefClientDelegate::onDownloadUpdated"
+++ "CCefClientDelegate::onDownloadUpdated"
DownloadManager::UpdateDownloadItem:   id:  1
   name:  ""
   path:  ""
   percent:  0 %,  4253692 / 0
   canceled:  false
   complete:  false
--- "CCefClientDelegate::onDownloadUpdated"
+++ "CCefClientDelegate::onDownloadUpdated"
DownloadManager::UpdateDownloadItem:   id:  1
   name:  ""
   path:  ""
   percent:  0 %,  4253692 / 32768
   canceled:  false
   complete:  false
--- "CCefClientDelegate::onDownloadUpdated"
+++ "CCefClientDelegate::onDownloadUpdated"
DownloadManager::UpdateDownloadItem:   id:  1
   name:  ""
   path:  ""
   percent:  0 %,  4253692 / 0
   canceled:  false
   complete:  false
--- "CCefClientDelegate::onDownloadUpdated"

同时，发现当useDefaultDialog形参为true时，不管路径为哪种形式，打开的对话框都是系统下载文件夹路径（路径可能会有差异），而不是指定的D:\\CppProject\\QCefView\\qtcharts-everywhere-opensource-src-5.15.9.tar.xz路径

item->start("D:\\CppProject\\QCefView\\qtcharts-everywhere-opensource-src-5.15.9.tar.xz", true);

如果不是bug，额外说明一下可能会更好。

Environment 【BUG产生的环境】

• OSR/NCW Mode: OSR
• OS & Version: Windows
• Qt Version: 5.15.2
• CEF Version: 102.0.10+gf249b2e+chromium-102.0.5005.115

Additional context 【更多额外信息】

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