GitLab

Check if ContentCaptureReceiver is valid before start capture.
Also, add a DCHECK() to the other call site of
ContentCaptureReceiverForFrame().

Bug: 1029678
Change-Id: Iaed486b6a7e9b322174e06fc0469defd5babb2c1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1947284Reviewed-by: Changwan Ryu <changwan@chromium.org>
Commit-Queue: Tao Bai <michaelbai@chromium.org>
Cr-Commit-Position: refs/heads/master@{#720729}