Move BitrateAllocation to api/ and rename it VideoBitrateAllocation

Since the webrtc_common build target does not have visibility set, we
cannot easily use BitrateAllocation in other parts of Chromium.
This is currently blocking parts of chromium:794608, and I know of other
usage outside webrtc already, so moving it to api/ should be warranted.

Also, since there's some naming confusion and this class is video
specific rename it VideoBitrateAllocation. This also fits with the
standard interface for producing these: VideoBitrateAllocator.

Bug: chromium:794608
Change-Id: I4c0fae40f9365e860c605a76a4f67ecc9b9cf9fe
Reviewed-on: https://webrtc-review.googlesource.com/70783
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Reviewed-by: Niels Moller <nisse@webrtc.org>
Commit-Queue: Erik Språng <sprang@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#22986}
diff --git a/modules/rtp_rtcp/source/rtcp_receiver_unittest.cc b/modules/rtp_rtcp/source/rtcp_receiver_unittest.cc
index 3c3c4b3..a7cbba1 100644
--- a/modules/rtp_rtcp/source/rtcp_receiver_unittest.cc
+++ b/modules/rtp_rtcp/source/rtcp_receiver_unittest.cc
@@ -93,7 +93,7 @@
     : public VideoBitrateAllocationObserver {
  public:
   MOCK_METHOD1(OnBitrateAllocationUpdated,
-               void(const BitrateAllocation& allocation));
+               void(const VideoBitrateAllocation& allocation));
 };
 
 // SSRC of remote peer, that sends rtcp packet to the rtcp receiver under test.
@@ -1318,7 +1318,7 @@
 }
 
 TEST_F(RtcpReceiverTest, ReceivesTargetBitrate) {
-  BitrateAllocation expected_allocation;
+  VideoBitrateAllocation expected_allocation;
   expected_allocation.SetBitrate(0, 0, 10000);
   expected_allocation.SetBitrate(0, 1, 20000);
   expected_allocation.SetBitrate(1, 0, 40000);
@@ -1348,7 +1348,7 @@
 }
 
 TEST_F(RtcpReceiverTest, HandlesIncorrectTargetBitrate) {
-  BitrateAllocation expected_allocation;
+  VideoBitrateAllocation expected_allocation;
   expected_allocation.SetBitrate(0, 0, 10000);
 
   rtcp::TargetBitrate bitrate;