UserAgent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:52.0) Gecko/20100101 Firefox/52.0

Steps to reproduce the problem:
1. Install chromium-browser on Kubuntu 16.04.2 and update everything to the latest version
2. Use a proxy that requires authentication and configure it from the KDE system setting
3. Launch chromium-browser and choose to "sign in" 
4. Notice a window pop-up and then the crash occcurs

What is the expected behavior?
 Sign in window should appear

What went wrong?
 Attach is the backtrace after installing the debug symbols package:

#0  0x00005555573104c1 in constrained_window::CreateWebModalDialogViews ()
#1  0x000055555731050f in constrained_window::ShowWebModalDialogViews ()
#2  0x0000555556bc8600 in LoginHandlerViews::BuildViewImpl ()
#3  0x00005555569db9ad in LoginHandler::ShowLoginPrompt ()
#4  0x00007ffff2060a50 in content::InterstitialPageImpl::OnDomOperationResponse () from /usr/lib/chromium-browser/./libcontent.so
#5  0x00007ffff2060b97 in content::InterstitialPageImpl::OnMessageReceived () from /usr/lib/chromium-browser/./libcontent.so
#6  0x00007ffff20893c3 in OnMessageReceived () from /usr/lib/chromium-browser/./libcontent.so
#7  0x00007ffff21f37b9 in OnMessageReceived () from /usr/lib/chromium-browser/./libcontent.so
#8  0x00007ffff352a984 in IPC::ChannelProxy::Context::OnDispatchMessage () from /usr/lib/chromium-browser/./libipc.so
#9  0x00007ffff78b7563 in base::debug::TaskAnnotator::RunTask () from /usr/lib/chromium-browser/./libbase.so
#10 0x00007ffff78dd760 in base::MessageLoop::RunTask () from /usr/lib/chromium-browser/./libbase.so
#11 0x00007ffff78df35d in base::MessageLoop::DeferOrRunPendingTask () from /usr/lib/chromium-browser/./libbase.so
#12 0x00007ffff78e01bd in base::MessageLoop::DoWork () from /usr/lib/chromium-browser/./libbase.so
#13 0x00007ffff78e0a79 in base::MessagePumpGlib::HandleDispatch () from /usr/lib/chromium-browser/./libbase.so
#14 0x00007ffff78e0abd in WorkSourceDispatch () from /usr/lib/chromium-browser/./libbase.so
#15 0x00007fffe55e7197 in g_main_context_dispatch () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#16 0x00007fffe55e73f0 in ?? () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#17 0x00007fffe55e749c in g_main_context_iteration () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#18 0x00007ffff78e080d in base::MessagePumpGlib::Run () from /usr/lib/chromium-browser/./libbase.so
#19 0x00007ffff78dcb42 in base::MessageLoop::RunHandler () from /usr/lib/chromium-browser/./libbase.so
#20 0x00007ffff79054d8 in base::RunLoop::Run () from /usr/lib/chromium-browser/./libbase.so
#21 0x0000555556014667 in ChromeBrowserMainParts::MainMessageLoopRun ()
#22 0x00007ffff1f9975f in content::BrowserMainLoop::RunMainMessageLoopParts () from /usr/lib/chromium-browser/./libcontent.so
#23 0x00007ffff1f9ba5d in content::BrowserMainRunnerImpl::Run () from /usr/lib/chromium-browser/./libcontent.so
#24 0x00007ffff1f953f9 in content::BrowserMain () from /usr/lib/chromium-browser/./libcontent.so
#25 0x00007ffff2608464 in content::ContentMainRunnerImpl::Run () from /usr/lib/chromium-browser/./libcontent.so
#26 0x00007ffff26078e1 in content::ContentMain () from /usr/lib/chromium-browser/./libcontent.so
#27 0x0000555555a6589c in ChromeMain ()
#28 0x00007fffe26ff830 in __libc_start_main (main=0x555555a639e0 <main()>, argc=2, argv=0x7fffffffdc88, init=<optimized out>, fini=<optimized out>, rtld_fini=<optimized out>, stack_end=0x7fffffffdc78) at ../csu/libc-start.c:291
#29 0x0000555555a65769 in _start ()

Crashed report ID: 

How much crashed? Whole browser

Is it a problem with a plugin? No 

Did this work before? N/A 

Chrome version: <Copy from: 'about:version'>  Channel: stable
OS Version: Kubuntu 16.04.2
Flash Version: Shockwave Flash 25.0 r0