Update audio_processing module

Corresponds to upstream commit 524e9b043e7e86fd72353b987c9d5f6a1ebf83e1

Update notes:

 * Pull in third party license file

 * Replace .gypi files with BUILD.gn to keep track of what changes
   upstream

 * Bunch of new filse pulled in as dependencies

 * Won't build yet due to changes needed on top of these

webrtc/system_wrappers/interface/thread_wrapper.h

@@ -0,0 +1,95 @@
+/*
+ *  Copyright (c) 2011 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.
+ */
+
+// System independant wrapper for spawning threads
+// Note: the spawned thread will loop over the callback function until stopped.
+// Note: The callback function is expected to return every 2 seconds or more
+// often.
+
+#ifndef WEBRTC_SYSTEM_WRAPPERS_INTERFACE_THREAD_WRAPPER_H_
+#define WEBRTC_SYSTEM_WRAPPERS_INTERFACE_THREAD_WRAPPER_H_
+
+#if defined(WEBRTC_WIN)
+#include <windows.h>
+#endif
+
+#include "webrtc/base/scoped_ptr.h"
+#include "webrtc/common_types.h"
+#include "webrtc/typedefs.h"
+
+namespace webrtc {
+
+// Callback function that the spawned thread will enter once spawned.
+// A return value of false is interpreted as that the function has no
+// more work to do and that the thread can be released.
+typedef bool(*ThreadRunFunction)(void*);
+
+enum ThreadPriority {
+#ifdef WEBRTC_WIN
+  kLowPriority = THREAD_PRIORITY_BELOW_NORMAL,
+  kNormalPriority = THREAD_PRIORITY_NORMAL,
+  kHighPriority = THREAD_PRIORITY_ABOVE_NORMAL,
+  kHighestPriority = THREAD_PRIORITY_HIGHEST,
+  kRealtimePriority = THREAD_PRIORITY_TIME_CRITICAL
+#else
+  kLowPriority = 1,
+  kNormalPriority = 2,
+  kHighPriority = 3,
+  kHighestPriority = 4,
+  kRealtimePriority = 5
+#endif
+};
+
+// Represents a simple worker thread.  The implementation must be assumed
+// to be single threaded, meaning that all methods of the class, must be
+// called from the same thread, including instantiation.
+// TODO(tommi): There's no need for this to be a virtual interface since there's
+// only ever a single implementation of it.
+class ThreadWrapper {
+ public:
+  virtual ~ThreadWrapper() {}
+
+  // Factory method. Constructor disabled.
+  //
+  // func        Pointer to a, by user, specified callback function.
+  // obj         Object associated with the thread. Passed in the callback
+  //             function.
+  // prio        Thread priority. May require root/admin rights.
+  // thread_name  NULL terminated thread name, will be visable in the Windows
+  //             debugger.
+  static rtc::scoped_ptr<ThreadWrapper> CreateThread(ThreadRunFunction func,
+      void* obj, const char* thread_name);
+
+  // Get the current thread's thread ID.
+  // NOTE: This is a static method. It returns the id of the calling thread,
+  // *not* the id of the worker thread that a ThreadWrapper instance represents.
+  // TODO(tommi): Move outside of the ThreadWrapper class to avoid confusion.
+  static uint32_t GetThreadId();
+
+  // Tries to spawns a thread and returns true if that was successful.
+  // Additionally, it tries to set thread priority according to the priority
+  // from when CreateThread was called. However, failure to set priority will
+  // not result in a false return value.
+  virtual bool Start() = 0;
+
+  // Stops the spawned thread and waits for it to be reclaimed with a timeout
+  // of two seconds. Will return false if the thread was not reclaimed.
+  // Multiple tries to Stop are allowed (e.g. to wait longer than 2 seconds).
+  // It's ok to call Stop() even if the spawned thread has been reclaimed.
+  virtual bool Stop() = 0;
+
+  // Set the priority of the worker thread.  Must be called when thread
+  // is running.
+  virtual bool SetPriority(ThreadPriority priority) = 0;
+};
+
+}  // namespace webrtc
+
+#endif  // WEBRTC_SYSTEM_WRAPPERS_INTERFACE_THREAD_WRAPPER_H_