Change the low-bitrate handling in BitrateControllerImpl

Changing to using strategy classes rather than having two different
derived classes of BitrateControllerImpl. This enables run-time switching
of the strategy, which is now possible through a new API. The reason is
that it must fit the current design of ViE.

BUG=2436
R=stefan@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/2789004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@5028 4adac7df-926f-26a2-2b94-8c16560cd09d
diff --git a/webrtc/modules/bitrate_controller/bitrate_controller_impl.h b/webrtc/modules/bitrate_controller/bitrate_controller_impl.h
index 5e56607..62ed6fd 100644
--- a/webrtc/modules/bitrate_controller/bitrate_controller_impl.h
+++ b/webrtc/modules/bitrate_controller/bitrate_controller_impl.h
@@ -23,30 +23,17 @@
 
 #include "webrtc/modules/bitrate_controller/send_side_bandwidth_estimation.h"
 #include "webrtc/system_wrappers/interface/critical_section_wrapper.h"
+#include "webrtc/system_wrappers/interface/scoped_ptr.h"
 
 namespace webrtc {
 
 class RtcpBandwidthObserverImpl;
+class LowRateStrategy;
 
 class BitrateControllerImpl : public BitrateController {
  public:
   friend class RtcpBandwidthObserverImpl;
 
-  explicit BitrateControllerImpl();
-  virtual ~BitrateControllerImpl();
-
-  virtual bool AvailableBandwidth(uint32_t* bandwidth) const OVERRIDE;
-
-  virtual RtcpBandwidthObserver* CreateRtcpBandwidthObserver() OVERRIDE;
-
-  virtual void SetBitrateObserver(BitrateObserver* observer,
-                                  const uint32_t start_bitrate,
-                                  const uint32_t min_bitrate,
-                                  const uint32_t max_bitrate) OVERRIDE;
-
-  virtual void RemoveBitrateObserver(BitrateObserver* observer) OVERRIDE;
-
- protected:
   struct BitrateConfiguration {
     BitrateConfiguration(uint32_t start_bitrate,
                          uint32_t min_bitrate,
@@ -72,6 +59,23 @@
       BitrateObserverConfiguration;
   typedef std::list<BitrateObserverConfiguration> BitrateObserverConfList;
 
+  explicit BitrateControllerImpl(bool enforce_min_bitrate);
+  virtual ~BitrateControllerImpl();
+
+  virtual bool AvailableBandwidth(uint32_t* bandwidth) const OVERRIDE;
+
+  virtual RtcpBandwidthObserver* CreateRtcpBandwidthObserver() OVERRIDE;
+
+  virtual void SetBitrateObserver(BitrateObserver* observer,
+                                  const uint32_t start_bitrate,
+                                  const uint32_t min_bitrate,
+                                  const uint32_t max_bitrate) OVERRIDE;
+
+  virtual void RemoveBitrateObserver(BitrateObserver* observer) OVERRIDE;
+
+  virtual void EnforceMinBitrate(bool enforce_min_bitrate) OVERRIDE;
+
+ private:
   // Called by BitrateObserver's direct from the RTCP module.
   void OnReceivedEstimatedBitrate(const uint32_t bitrate);
 
@@ -80,10 +84,6 @@
                                     const int number_of_packets,
                                     const uint32_t now_ms);
 
-  SendSideBandwidthEstimation bandwidth_estimation_;
-  BitrateObserverConfList bitrate_observers_;
-
- private:
   typedef std::multimap<uint32_t, ObserverConfiguration*> ObserverSortingMap;
 
   BitrateObserverConfList::iterator
@@ -91,13 +91,11 @@
   void OnNetworkChanged(const uint32_t bitrate,
                         const uint8_t fraction_loss,  // 0 - 255.
                         const uint32_t rtt);
-  // Derived classes must implement this strategy method.
-  virtual void LowRateAllocation(uint32_t bitrate,
-                                 uint8_t fraction_loss,
-                                 uint32_t rtt,
-                                 uint32_t sum_min_bitrates) = 0;
 
   CriticalSectionWrapper* critsect_;
+  SendSideBandwidthEstimation bandwidth_estimation_;
+  BitrateObserverConfList bitrate_observers_;
+  scoped_ptr<LowRateStrategy> low_rate_strategy_;
 };
 }  // namespace webrtc
 #endif  // WEBRTC_MODULES_BITRATE_CONTROLLER_BITRATE_CONTROLLER_IMPL_H_