ContentCapture: Notify of session end when RFH is destroyed

This patch includes below changes:

Removed ContentCaptureConsumer.destory() method since it shall be
still available when WebContents is being destoryed, so
ContentCaptureReceiver can send the session removed message.

Used last reported session instead of current one for removing
session.

Bug: 970330
Change-Id: Ie3f5961ff4dcb02335a02da700c32f41e337b92c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1660783
Reviewed-by: Changwan Ryu <changwan@chromium.org>
Reviewed-by: Ted Choc <tedchoc@chromium.org>
Commit-Queue: Tao Bai <michaelbai@chromium.org>
Cr-Commit-Position: refs/heads/master@{#672269}
10 files changed