Fixed rtcp rpsi parsing of invalid packets.

Fixed rtcp rpsi parsing of invalid packets.
Parsing is done in one Iterate instead of two
  preventing handling two half-valid (invalid) rpsi packets as one valid,
  making test parser calculate rpsi packet once instead of twice.
Added check padding bits doesn't exceed native bit string length.
Marking rpsi received moved after it is validated.

BUG=600977

[danilchap, 2016-04-07 12:31:33]

danilchap@webrtc.org changed reviewers:
+ asapersson@webrtc.org

[åsapersson, 2016-04-11 09:22:55]

https://codereview.webrtc.org/1870573004/diff/20001/webrtc/modules/rtp_rtcp/s...
File webrtc/modules/rtp_rtcp/source/rtcp_receiver.cc (left):

https://codereview.webrtc.org/1870573004/diff/20001/webrtc/modules/rtp_rtcp/s...
webrtc/modules/rtp_rtcp/source/rtcp_receiver.cc:1104: if (pktType ==
RTCPPacketTypes::kPsfbRpsi) {
kPsfbRpsiItem?

https://codereview.webrtc.org/1870573004/diff/20001/webrtc/modules/rtp_rtcp/s...
File webrtc/modules/rtp_rtcp/source/rtcp_receiver_unittest.cc (right):

https://codereview.webrtc.org/1870573004/diff/20001/webrtc/modules/rtp_rtcp/s...
webrtc/modules/rtp_rtcp/source/rtcp_receiver_unittest.cc:167: 
Would also be good to tests a valid rpsi packet.

https://codereview.webrtc.org/1870573004/diff/20001/webrtc/modules/rtp_rtcp/s...
webrtc/modules/rtp_rtcp/source/rtcp_receiver_unittest.cc:192:
TEST_F(RtcpReceiverTest, TooHalfValidRpsiAreIgnored) {
Too->Two

https://codereview.webrtc.org/1870573004/diff/20001/webrtc/modules/rtp_rtcp/s...
File webrtc/modules/rtp_rtcp/source/rtcp_utility.cc (left):

https://codereview.webrtc.org/1870573004/diff/20001/webrtc/modules/rtp_rtcp/s...
webrtc/modules/rtp_rtcp/source/rtcp_utility.cc:1337: _packetType =
RTCPPacketTypes::kPsfbRpsi;
Should the packet type be set to kPsfbRpsiItem here?
(And remove changes above?)

[danilchap, 2016-04-11 11:00:31]

https://codereview.webrtc.org/1870573004/diff/20001/webrtc/modules/rtp_rtcp/s...
File webrtc/modules/rtp_rtcp/source/rtcp_receiver.cc (left):

https://codereview.webrtc.org/1870573004/diff/20001/webrtc/modules/rtp_rtcp/s...
webrtc/modules/rtp_rtcp/source/rtcp_receiver.cc:1104: if (pktType ==
RTCPPacketTypes::kPsfbRpsi) {
On 2016/04/11 09:22:55, åsapersson wrote:
> kPsfbRpsiItem?

For neighbor packets 'Item' suffix means subpacket, FCI item.
For Rpsi packet this notion removed (because valid packet has exactly one FCI
item, it make little sense to handle rpsi item without rpsi)

https://codereview.webrtc.org/1870573004/diff/20001/webrtc/modules/rtp_rtcp/s...
File webrtc/modules/rtp_rtcp/source/rtcp_receiver_unittest.cc (right):

https://codereview.webrtc.org/1870573004/diff/20001/webrtc/modules/rtp_rtcp/s...
webrtc/modules/rtp_rtcp/source/rtcp_receiver_unittest.cc:167: 
On 2016/04/11 09:22:55, åsapersson wrote:
> Would also be good to tests a valid rpsi packet.

Done.

https://codereview.webrtc.org/1870573004/diff/20001/webrtc/modules/rtp_rtcp/s...
webrtc/modules/rtp_rtcp/source/rtcp_receiver_unittest.cc:192:
TEST_F(RtcpReceiverTest, TooHalfValidRpsiAreIgnored) {
On 2016/04/11 09:22:55, åsapersson wrote:
> Too->Two

oops, Done

https://codereview.webrtc.org/1870573004/diff/20001/webrtc/modules/rtp_rtcp/s...
File webrtc/modules/rtp_rtcp/source/rtcp_utility.cc (left):

https://codereview.webrtc.org/1870573004/diff/20001/webrtc/modules/rtp_rtcp/s...
webrtc/modules/rtp_rtcp/source/rtcp_utility.cc:1337: _packetType =
RTCPPacketTypes::kPsfbRpsi;
On 2016/04/11 09:22:55, åsapersson wrote:
> Should the packet type be set to kPsfbRpsiItem here?
> (And remove changes above?)

It is set to kPsfbRpsi in the very end of the function, after validating padding
size.
To Indicate parsing single item finish parsing packet, function renamed to
ParseRPSI.
Either way (valid and invalid) parser stay in the 'TopLevel' state and doesn't
need to enter/leave intermediate state.