Adding two tests: 
1. Bitrate allocation strategy unit test 
2. Perf test determining minimal supported bitrate with and without strategy

Bug: webrtc:8243
Change-Id: Idf675fbadddb66c77b2582052d6497971eb99ad6
Reviewed-on: https://webrtc-review.googlesource.com/4880
Reviewed-by: Stefan Holmer <stefan@webrtc.org>
Reviewed-by: Niels Moller <nisse@webrtc.org>
Reviewed-by: Taylor Brandstetter <deadbeef@webrtc.org>
Commit-Queue: Alex Narest <alexnarest@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#20886}
diff --git a/rtc_base/BUILD.gn b/rtc_base/BUILD.gn
index 873a3eb..ae4101c 100644
--- a/rtc_base/BUILD.gn
+++ b/rtc_base/BUILD.gn
@@ -860,6 +860,7 @@
       "basictypes_unittest.cc",
       "bind_unittest.cc",
       "bitbuffer_unittest.cc",
+      "bitrateallocationstrategy_unittest.cc",
       "buffer_unittest.cc",
       "bufferqueue_unittest.cc",
       "bytebuffer_unittest.cc",