Adding a new ramp-up-down-up test

The new test is based upon the exisiting rampup test, but also adds
a low-rate period. The main purpose of the test is to verify the
SuspendBelowMinBitrate functionality, which must be enabled for the
test to pass.

The CL also adds a change to the min bitrate in the send-side bandwidth
estimator when SuspendBelowMinBitrate is enabled.

An anonymous namespace is added around the StreamObserver classes
in the test to avoid silent linker conflicts that could happen
otherwise.

Note: this CL depends on https://webrtc-codereview.appspot.com/9049004/

BUG=2636
R=stefan@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/9059004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@5646 4adac7df-926f-26a2-2b94-8c16560cd09d
diff --git a/webrtc/modules/bitrate_controller/bitrate_controller_impl.cc b/webrtc/modules/bitrate_controller/bitrate_controller_impl.cc
index c2c8616..f4f085c 100644
--- a/webrtc/modules/bitrate_controller/bitrate_controller_impl.cc
+++ b/webrtc/modules/bitrate_controller/bitrate_controller_impl.cc
@@ -249,6 +249,11 @@
   }
 }
 
+void BitrateControllerImpl::SetBweMinBitrate(uint32_t min_bitrate) {
+  CriticalSectionScoped cs(critsect_);
+  bandwidth_estimation_.SetMinBitrate(min_bitrate);
+}
+
 void BitrateControllerImpl::OnReceivedEstimatedBitrate(const uint32_t bitrate) {
   uint32_t new_bitrate = 0;
   uint8_t fraction_lost = 0;