media: Enable EncryptedMediaHdcpPolicyCheck by default

- Remove the origin trial
- Mark the status as "stable"

Blink intent-to-ship approval at
https://groups.google.com/a/chromium.org/d/msg/blink-dev/w0jNaAhyTV0/3oDkR_ASAQAJ

TBR=timvolodine

Bug: 709348
Test: Manually tested to make sure the API is available by default.
Change-Id: I84306dc0e17f104043fa2205529e650e255e7175
Reviewed-on: https://chromium-review.googlesource.com/c/1423090
Commit-Queue: Xiaohan Wang <xhwang@chromium.org>
Reviewed-by: Philip Jägenstedt <foolip@chromium.org>
Cr-Commit-Position: refs/heads/master@{#625807}
4 files changed