Able to reproduce this issue on Ubuntu 14.04 using chrome latest dev #61.0.3129.0. No crashes observed on Mac OS 10.12.5 and Windows-10. 

Stack Trace:
-------------
Thread 46 (id: 20887) CRASHED [SIGABRT @ 0x000003e800004345 ] MAGIC SIGNATURE THREAD
Stack Quality24%Show frame trust levels
0x00007f0a23663c37	(libc-2.19.so + 0x00036c37 )	
0x00007f0a23667027	(libc-2.19.so + 0x0003a027 )	
0x00007f0a237ad143	(libc-2.19.so + 0x00180143 )	
0x00007f0a286bb1da	(libX11.so.6.3.0 + 0x000ab1da )	
0x00007f0a2365e552	(libc-2.19.so + 0x00031552 )	
0x00007f0a286bb20c	(libX11.so.6.3.0 + 0x000ab20c )	
0x00007f0a286bb6af	(libX11.so.6.3.0 + 0x000ab6af )	
0x00007f0a237b0bf7	(libc-2.19.so + 0x00183bf7 )	
0x00007f0a2365cbf5	(libc-2.19.so + 0x0002fbf5 )	
0x00007f0a286bb6af	(libX11.so.6.3.0 + 0x000ab6af )	
0x00007f0a237ad143	(libc-2.19.so + 0x00180143 )	
0x00007f0a286bb20c	(libX11.so.6.3.0 + 0x000ab20c )	
0x00007f0a286bb1da	(libX11.so.6.3.0 + 0x000ab1da )	
0x00007f0a286bb6af	(libX11.so.6.3.0 + 0x000ab6af )	
0x00007f0a286bb20c	(libX11.so.6.3.0 + 0x000ab20c )	
0x00007f0a286bb6af	(libX11.so.6.3.0 + 0x000ab6af )	
0x00007f0a286bb20c	(libX11.so.6.3.0 + 0x000ab20c )	
0x00007f0a286bb1da	(libX11.so.6.3.0 + 0x000ab1da )	
0x00007f0a2365cca1	(libc-2.19.so + 0x0002fca1 )	
0x00007f0a286bb20c	(libX11.so.6.3.0 + 0x000ab20c )	
0x00007f0a2864b79b	(libX11.so.6.3.0 + 0x0003b79b )	
0x00007f0a2864c5c2	(libX11.so.6.3.0 + 0x0003c5c2 )	
0x00007f0a286480cc	(libX11.so.6.3.0 + 0x000380cc )	
0x0000563eb9ad8349	(chrome -x_server_pixel_buffer.cc:327 )	webrtc::XServerPixelBuffer::CaptureRect(webrtc::DesktopRect const&, webrtc::DesktopFrame*)
0x0000563eb9ad5c5b	(chrome -screen_capturer_x11.cc:343 )	webrtc::(anonymous namespace)::ScreenCapturerLinux::CaptureFrame()
0x0000563eb9e62657	(chrome -native_desktop_media_list.cc:178 )	NativeDesktopMediaList::Worker::RefreshThumbnails(std::vector<content::DesktopMediaID, std::allocator<content::DesktopMediaID> > const&, gfx::Size const&)
0x0000563eb818d5af	(chrome -callback.h:91 )	base::debug::TaskAnnotator::RunTask(char const*, base::PendingTask*)
0x0000563eb81c808f	(chrome -task_tracker.cc:331 )	base::internal::TaskTracker::PerformRunTask(std::unique_ptr<base::internal::Task, std::default_delete<base::internal::Task> >, base::internal::Sequence*)
0x0000563eb81c8b3f	(chrome -task_tracker_posix.cc:22 )	base::internal::TaskTrackerPosix::PerformRunTask(std::unique_ptr<base::internal::Task, std::default_delete<base::internal::Task> >, base::internal::Sequence*)
0x0000563eb81c89ca	(chrome -task_tracker.cc:250 )	base::internal::TaskTracker::RunNextTask(base::internal::Sequence*)
0x0000563eb81c482c	(chrome -scheduler_worker.cc:80 )	base::internal::SchedulerWorker::Thread::ThreadMain()
0x0000563eb81d13d3	(chrome -platform_thread_posix.cc:71 )	base::(anonymous namespace)::ThreadFunc(void*)
0x00007f0a29a17183	(libpthread-2.19.so + 0x00008183 )	
0x00007f0a2372abec	(libc-2.19.so + 0x000fdbec )	

Issue is also seen in todays dev candidate i.e:61.0.3128.0 

Manual bisect info:
=======================
Good Build:61.0.3124.0 
Bad Build:61.0.3125.0  

Used code search for the file "native_desktop_media_list.cc" from above stack trace and suspecting the below change
https://chromium.googlesource.com/chromium/src/+/35ec1444165dcb7f1416251d634e43b1950d1e20

sergeyu@: Could you please check if this is caused with respect to your change, if not please help us in reassign the issue to the right owner. 

Note: Since this is a recent regression observed on M61 adding RB-Dev please feel free to edit if this is not the case.

Thanks! 

Spoke with sergeyu@ offline and he is working on a fix since the revert has other dependencies. I will request a merge to 3128 branch once the fix has been landed in trunk.

Thank you!

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/76ea4f567679fb6bdbe02d34bd6d57a66e02657b

commit 76ea4f567679fb6bdbe02d34bd6d57a66e02657b
Author: Sergey Ulanov <sergeyu@chromium.org>
Date: Tue Jun 13 18:47:09 2017

Fix crash in DesktopCapture API

After crrev.com/478081 the same DesktopCaptureOptions were used for
screen and window capturer. This means that the same X display was
used on different threads, which is not supported.

BUG= 732695 

Change-Id: Ife46591ec8bf660e3675990867b578b8de4909e7
Reviewed-on: https://chromium-review.googlesource.com/534173
Reviewed-by: Zijie He <zijiehe@chromium.org>
Cr-Commit-Position: refs/heads/master@{#479080}
[modify] https://crrev.com/76ea4f567679fb6bdbe02d34bd6d57a66e02657b/chrome/browser/extensions/api/desktop_capture/desktop_capture_base.cc

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/5b6764f355d00b6a82fbdf764b136db855a1cd6d

commit 5b6764f355d00b6a82fbdf764b136db855a1cd6d
Author: Sergey Ulanov <sergeyu@chromium.org>
Date: Tue Jun 13 18:51:08 2017

Fix crash in DesktopCapture API

After crrev.com/478081 the same DesktopCaptureOptions were used for
screen and window capturer. This means that the same X display was
used on different threads, which is not supported.

BUG= 732695 
TBR=sergeyu@chromium.org

(cherry picked from commit 76ea4f567679fb6bdbe02d34bd6d57a66e02657b)

Change-Id: Ife46591ec8bf660e3675990867b578b8de4909e7
Reviewed-on: https://chromium-review.googlesource.com/534173
Reviewed-by: Zijie He <zijiehe@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#479080}
Reviewed-on: https://chromium-review.googlesource.com/534213
Reviewed-by: Sergey Ulanov <sergeyu@chromium.org>
Cr-Commit-Position: refs/branch-heads/3128@{#3}
Cr-Branched-From: 4138c6d4e9f036df01c2a6092a242a3aa39b6afc-refs/heads/master@{#478527}
[modify] https://crrev.com/5b6764f355d00b6a82fbdf764b136db855a1cd6d/chrome/browser/extensions/api/desktop_capture/desktop_capture_base.cc

should be fixed now

Thank you sergeyu@ for quick fix and merge and Thank you manoranjanr@ for follow up. I'm triggering Linux Dev build from branch 3128.

The above fix is working as intended on Latest Dev#61.0.3128.3 for Linux Ubuntu 14.04.