media: Don't idle suspend the pipeline when in fullscreen

There's no need to suspend in fullscreen, so by avoiding it we can
save a bit of time when playback is resumed.

BUG=602436

Review URL: https://codereview.chromium.org/1880713002

Cr-Commit-Position: refs/heads/master@{#386530}
3 files changed