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/rw_lock_generic.cc

@@ -0,0 +1,77 @@
+/*
+ *  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/source/rw_lock_generic.h"
+
+#include "webrtc/system_wrappers/interface/condition_variable_wrapper.h"
+#include "webrtc/system_wrappers/interface/critical_section_wrapper.h"
+
+namespace webrtc {
+
+RWLockGeneric::RWLockGeneric()
+    : readers_active_(0),
+      writer_active_(false),
+      readers_waiting_(0),
+      writers_waiting_(0) {
+  critical_section_ = CriticalSectionWrapper::CreateCriticalSection();
+  read_condition_ = ConditionVariableWrapper::CreateConditionVariable();
+  write_condition_ = ConditionVariableWrapper::CreateConditionVariable();
+}
+
+RWLockGeneric::~RWLockGeneric() {
+  delete write_condition_;
+  delete read_condition_;
+  delete critical_section_;
+}
+
+void RWLockGeneric::AcquireLockExclusive() {
+  CriticalSectionScoped cs(critical_section_);
+  if (writer_active_ || readers_active_ > 0) {
+    ++writers_waiting_;
+    while (writer_active_ || readers_active_ > 0) {
+      write_condition_->SleepCS(*critical_section_);
+    }
+    --writers_waiting_;
+  }
+  writer_active_ = true;
+}
+
+void RWLockGeneric::ReleaseLockExclusive() {
+  CriticalSectionScoped cs(critical_section_);
+  writer_active_ = false;
+  if (writers_waiting_ > 0) {
+    write_condition_->Wake();
+  } else if (readers_waiting_ > 0) {
+    read_condition_->WakeAll();
+  }
+}
+
+void RWLockGeneric::AcquireLockShared() {
+  CriticalSectionScoped cs(critical_section_);
+  if (writer_active_ || writers_waiting_ > 0) {
+    ++readers_waiting_;
+
+    while (writer_active_ || writers_waiting_ > 0) {
+      read_condition_->SleepCS(*critical_section_);
+    }
+    --readers_waiting_;
+  }
+  ++readers_active_;
+}
+
+void RWLockGeneric::ReleaseLockShared() {
+  CriticalSectionScoped cs(critical_section_);
+  --readers_active_;
+  if (readers_active_ == 0 && writers_waiting_ > 0) {
+    write_condition_->Wake();
+  }
+}
+
+}  // namespace webrtc