media-internals: Fix audio update logic.

media-internals: Fix audio update logic.

This fixes a regression introduced in r333285. Even if CanUpdate() is false, we
should still go through the full logic to update |audio_streams_cached_data_| so
that future UpdateAudioLog() calls will include the previous data.

Also rename SendAudioLogUpdate() to UpdateAudioLog() to better reflect it's
intent (which confused me when I worked on r333285).

BUG=260005
TEST=Manually tested as follows:
1. Start a youtube video in one tab.
2. Start a chrome://media-internals page in another tab.
3. Navigate to "Audio" tab in the chrome://media-internals page.
4. You should be able to see an audio controler and an audio stream.

Review URL: https://codereview.chromium.org/1184093006

Cr-Commit-Position: refs/heads/master@{#334541}