I have experience a weird issue by BrowserLink feature.
A simple webforms page (Default.aspx) with Iframe src (FileUpload.aspx).
On Visual Studio 2015 Community Editon (Update 3), Enable BrowserLink, then Start Debugging or Start Without Debugging to launch the web page.
If i select a images file on FileUpload.aspx and press save button to perform FileUpload1.SaveAs("xxx") method, the full web page include iframe and parent page will reload.
However, if i select a text file to upload instead, only Iframe will postback that as expect result.
This is so weird, the postback behaviour can be different by upload file type.
I disable the Browserlink, the problem also gone.
I create a simple screencast and sample project. This is a serious problem to me. 
Screen record video https://youtu.be/weHc4Twelns
Sample Project https://www.sendspace.com/file/1ca3yq