Revert of Cast: Re-factor rtcp_sender.cc into rtcp_builder.cc and do some cleanup

Revert of Cast: Re-factor rtcp_sender.cc into rtcp_builder.cc and do some cleanup (patchset #3 id:40001 of https://codereview.chromium.org/513313004/)

Reason for revert:
Caused cast_unittest rtcp test failures on Linux Asan Lsan builders (memory leaks).

http://build.chromium.org/p/chromium.memory/builders/Linux%20ASan%20LSan%20Tests%20%282%29/builds/7132


Original issue's description:
> Cast: Re-factor rtcp_sender.cc into rtcp_builder.cc and do some cleanup
> 
> Committed: https://chromium.googlesource.com/chromium/src/+/6217e450d9e75037c62fff773c94aebe7f3ed2e6

TBR=miu@chromium.org,hubbe@chromium.org
NOTREECHECKS=true
NOTRY=true

Committed: https://crrev.com/6cdfc247ea7233ffd1eda000eb4ada794508eedd
Cr-Commit-Position: refs/heads/master@{#293665}

[Noel Gordon, 2014-09-07 20:39:02]

Created Revert of Cast: Re-factor rtcp_sender.cc into rtcp_builder.cc and do
some cleanup

[commit-bot: I haz the power, 2014-09-07 20:39:29]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/noel@chromium.org/541293004/1

[commit-bot: I haz the power, 2014-09-07 20:41:21]

Committed patchset #1 (id:1) as c25e54eb09c4bb26377548695a2ca90d5ffd9eeb

[commit-bot: I haz the power, 2014-09-10 03:44:19]

Patchset 1 (id:??) landed as
https://crrev.com/6cdfc247ea7233ffd1eda000eb4ada794508eedd
Cr-Commit-Position: refs/heads/master@{#293665}