Bit more details:
- This is the CL that enables capture from offscreen canvas: https://codereview.chromium.org/2632593003/ 
- The problem only happens when we use transferFromImageBitmap().
- Capture doesn't stop working but the frame rate dropped dramatically over the week. I found out that reverting the suspected CL, https://codereview.chromium.org/2625873005 , helps. 

It looks like the issue can be fixed by basically commenting out the status check after calling getSourceImageForCanvas(). The value of it is garbage, which looks there is an implementation which doesn't set status.
https://cs.chromium.org/chromium/src/third_party/WebKit/Source/core/html/HTMLCanvasElement.cpp?rcl=0&l=514

I found it out while adding the content_browsertest below which I will add to offscreen canvas capture CL. Let me know when it would be good time go back to it.
https://codereview.chromium.org/2657773004/

This is due to not setting |status| below. It happens for ImageBitmapRenderingContext cases, so I will merge with  issue 679610  and work on a fix. 
https://cs.chromium.org/chromium/src/third_party/WebKit/Source/core/html/HTMLCanvasElement.cpp?rcl=1b08639b651c7514b61d6b905f61719b40d4b3c6&l=1264