debugger: Abandon context when Qt changes it without notice

Qt changes the context on many conditions. Abandon GrContext
in these cases.

Also call GrContext::resetContext during Qt GL paint callback,
the GL state may be touched by Qt.

Fixes the bug where changing between gpu and msaa would start
erroring in framebuffer binds, if the .skp had many layers.

Review URL: https://codereview.chromium.org/915573002
1 file changed