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/source/event.cc

@@ -0,0 +1,54 @@
+/*
+ *  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.
+ */
+
+#include "webrtc/system_wrappers/interface/event_wrapper.h"
+
+#if defined(_WIN32)
+#include <windows.h>
+#include "webrtc/system_wrappers/source/event_timer_win.h"
+#elif defined(WEBRTC_MAC) && !defined(WEBRTC_IOS)
+#include <ApplicationServices/ApplicationServices.h>
+#include <pthread.h>
+#include "webrtc/system_wrappers/source/event_timer_posix.h"
+#else
+#include <pthread.h>
+#include "webrtc/system_wrappers/source/event_timer_posix.h"
+#endif
+
+#include "webrtc/base/event.h"
+
+namespace webrtc {
+
+class EventWrapperImpl : public EventWrapper {
+ public:
+  EventWrapperImpl() : event_(false, false) {}
+  ~EventWrapperImpl() override {}
+
+  bool Set() override {
+    event_.Set();
+    return true;
+  }
+
+  EventTypeWrapper Wait(unsigned long max_time) override {
+    int to_wait = max_time == WEBRTC_EVENT_INFINITE ?
+        rtc::Event::kForever : static_cast<int>(max_time);
+    return event_.Wait(to_wait) ? kEventSignaled : kEventTimeout;
+  }
+
+ private:
+  rtc::Event event_;
+};
+
+// static
+EventWrapper* EventWrapper::Create() {
+  return new EventWrapperImpl();
+}
+
+}  // namespace webrtc