Rollup of AudioManager crash fixes from henrika.

fc3da74 Fixes crash in AudioManagerMac at shutdown.
03262d2 Avoids accessing Core Audio APIs during shutdown
5e09960 Prevents crash in media::AudioInputController::OnData in Mac at shutdown

BUG=623703, 626512
TEST=none

(cherry picked from commit 8f02cec97c98bafdc9fcb07f812efe8d9635a0fc)

Review URL: https://codereview.chromium.org/2147613004 .

Cr-Commit-Position: refs/branch-heads/2785@{#98}
Cr-Branched-From: 68623971be0cfc492a2cb0427d7f478e7b214c24-refs/heads/master@{#403382}
3 files changed