DO NOT MERGE: Cherry picked hacks to better hide A/V sync issues.

Squashed commit of the following:

commit b1732e9b8bfea4c99bd07907c9aac9fcf1e8b264
Author: Andreas Huber <andih@google.com>
Date:   Thu Feb 24 12:05:40 2011 -0800

    DO NOT MERGE: Alternate patch for late video issue: seek only the video ahead to the next

    syncframe after the current audio media position, leave audio untouched.

    Change-Id: I4f6eb4e577147bc12ed2e998bea299f4bcfaf936
    related-to-bug: 3375737

commit 5e7282cf0b5c7a613da5e65fd6c8cb33a1058f8e
Author: Andreas Huber <andih@google.com>
Date:   Fri Feb 11 13:09:36 2011 -0800

    DO NOT MERGE: Start playing (and decoding) audio only after the first video frame has been decoded.

    if there's both audio and video content. This gives the video decoder an opportunity
    to fill its internal buffer queue at the start of playback.

    Change-Id: If17c4243546b1c27c8e5ee43941654d0e36f5ee5
    related-to-bug: 3431702

Change-Id: Ic3a6be467ff7ad09da04b1d2bb1a692ee38002b4