Cast:refactor RTCP to clang format

This cl is pure style-targeted refactoring. 
No functional changes were made. 

BUG=339176

Review URL: https://codereview.chromium.org/133793007

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@248082 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 248082