Reland "Moved congestion controller to goog_cc folder."

This is a reland of e6cefdf9c572cdce55ff0497ad6e516c76132ee8.

Original change's description:
> Moved congestion controller to goog_cc folder.
> 
> Bug: webrtc:8415
> Change-Id: I2070da0cacf1dbfc4b6a89285af3e68fd03497ab
> Reviewed-on: https://webrtc-review.googlesource.com/43841
> Commit-Queue: Sebastian Jansson <srte@webrtc.org>
> Reviewed-by: Björn Terelius <terelius@webrtc.org>
> Reviewed-by: Stefan Holmer <stefan@webrtc.org>
> Cr-Commit-Position: refs/heads/master@{#21928}

Bug: webrtc:8415
Change-Id: Ib5cf8641466655d64ac80f720561817f4cab49a9
Reviewed-on: https://webrtc-review.googlesource.com/53062
Commit-Queue: Sebastian Jansson <srte@webrtc.org>
Reviewed-by: Björn Terelius <terelius@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#22244}

modules/congestion_controller/goog_cc/probe_controller.h

@@ -0,0 +1,100 @@
+/*
+ *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef MODULES_CONGESTION_CONTROLLER_GOOG_CC_PROBE_CONTROLLER_H_
+#define MODULES_CONGESTION_CONTROLLER_GOOG_CC_PROBE_CONTROLLER_H_
+
+#include <stdint.h>
+
+#include <initializer_list>
+
+#include "api/optional.h"
+#include "modules/congestion_controller/network_control/include/network_control.h"
+
+namespace webrtc {
+
+class Clock;
+
+namespace webrtc_cc {
+
+// This class controls initiation of probing to estimate initial channel
+// capacity. There is also support for probing during a session when max
+// bitrate is adjusted by an application.
+class ProbeController {
+ public:
+  explicit ProbeController(NetworkControllerObserver* observer);
+  ~ProbeController();
+
+  void SetBitrates(int64_t min_bitrate_bps,
+                   int64_t start_bitrate_bps,
+                   int64_t max_bitrate_bps,
+                   int64_t at_time_ms);
+
+  void OnNetworkAvailability(NetworkAvailability msg);
+
+  void SetEstimatedBitrate(int64_t bitrate_bps, int64_t at_time_ms);
+
+  void EnablePeriodicAlrProbing(bool enable);
+
+  void SetAlrStartTimeMs(rtc::Optional<int64_t> alr_start_time);
+  void SetAlrEndedTimeMs(int64_t alr_end_time);
+
+  void RequestProbe(int64_t at_time_ms);
+
+  // Resets the ProbeController to a state equivalent to as if it was just
+  // created EXCEPT for |enable_periodic_alr_probing_|.
+  void Reset(int64_t at_time_ms);
+
+  void Process(int64_t at_time_ms);
+
+ private:
+  enum class State {
+    // Initial state where no probing has been triggered yet.
+    kInit,
+    // Waiting for probing results to continue further probing.
+    kWaitingForProbingResult,
+    // Probing is complete.
+    kProbingComplete,
+  };
+
+  void InitiateExponentialProbing(int64_t at_time_ms);
+  void InitiateProbing(int64_t now_ms,
+                       std::initializer_list<int64_t> bitrates_to_probe,
+                       bool probe_further);
+
+  NetworkControllerObserver* const observer_;
+
+  bool network_available_;
+  State state_;
+  int64_t min_bitrate_to_probe_further_bps_;
+  int64_t time_last_probing_initiated_ms_;
+  int64_t estimated_bitrate_bps_;
+  int64_t start_bitrate_bps_;
+  int64_t max_bitrate_bps_;
+  int64_t last_bwe_drop_probing_time_ms_;
+  rtc::Optional<int64_t> alr_start_time_ms_;
+  rtc::Optional<int64_t> alr_end_time_ms_;
+  bool enable_periodic_alr_probing_;
+  int64_t time_of_last_large_drop_ms_;
+  int64_t bitrate_before_last_large_drop_bps_;
+
+  bool in_rapid_recovery_experiment_;
+  // For WebRTC.BWE.MidCallProbing.* metric.
+  bool mid_call_probing_waiting_for_result_;
+  int64_t mid_call_probing_bitrate_bps_;
+  int64_t mid_call_probing_succcess_threshold_;
+
+  RTC_DISALLOW_IMPLICIT_CONSTRUCTORS(ProbeController);
+};
+
+}  // namespace webrtc_cc
+}  // namespace webrtc
+
+#endif  // MODULES_CONGESTION_CONTROLLER_GOOG_CC_PROBE_CONTROLLER_H_