Log statistics on CPU usage in Hz in addition to wall clock time Use CPU statistics for all playback threads, not just MIXER (but they are disabled by default by a compile-time debug macro). ThreadCpuUsage library: - Move statistics out of the library and leave that up to the caller - Add API to determine a CPU's frequency Change-Id: Ia1011123146e641fcf210ef26e78ae2b4d3b64ad