[Cast] Aggressively send sender reports until first receiver report is received.

[Cast] Aggressively send sender reports until first receiver report is received.

Identical logic change in both AudioSender and VideoSender: Send a sender
report just before each frame, up to the first 100 frames.  Then, they are
sent at ~1 second intervals thereafter.  However, if a receiver report
shows up, we halt the aggressive report sending immediately since we know
the data dependency (receiver side) has been satisfied.

Also, misc clean-ups:

1. RtpTimestampHelper threw away significant precision in its calculations
   (was truncating to millis).
2. Unit tests were using EXPECT with args in the wrong order (per gtest
   requirements).
3. Got rid of useless LocalRtcpXXXXXSenderFeedback class.

BUG=371482
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=272732

[miu, 2014-05-23 22:41:28]

hubbe: PTAL.

https://codereview.chromium.org/295603004/diff/20001/media/cast/rtp_timestamp...
File media/cast/rtp_timestamp_helper.cc (left):

https://codereview.chromium.org/295603004/diff/20001/media/cast/rtp_timestamp...
media/cast/rtp_timestamp_helper.cc:23: *rtp_timestamp = last_rtp_timestamp_ +
elapsed_time.InMilliseconds() *
Not sure whether this was hurting anything, but the truncation in precision
(micros-->millis) irritated me too much.

[hubbe, 2014-05-23 22:47:33]

https://codereview.chromium.org/295603004/diff/20001/media/cast/rtp_timestamp...
File media/cast/rtp_timestamp_helper.cc (right):

https://codereview.chromium.org/295603004/diff/20001/media/cast/rtp_timestamp...
media/cast/rtp_timestamp_helper.cc:24: elapsed_time * frequency_ /
base::TimeDelta::FromSeconds(1);
I think this will wrap around actually...

[hubbe, 2014-05-23 22:51:23]

lgtm

[miu, 2014-05-23 22:51:36]

The CQ bit was checked by miu@chromium.org

[commit-bot: I haz the power, 2014-05-23 22:53:23]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/miu@chromium.org/295603004/20001

[Alpha Left Google, 2014-05-23 23:00:06]

LGTM to me too.

[commit-bot: I haz the power, 2014-05-24 13:05:27]

Change committed as 272732