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/modules/audio_processing/transient/wpd_tree.h

@@ -0,0 +1,91 @@
+/*
+ *  Copyright (c) 2013 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 WEBRTC_MODULES_AUDIO_PROCESSING_TRANSIENT_WPD_TREE_H_
+#define WEBRTC_MODULES_AUDIO_PROCESSING_TRANSIENT_WPD_TREE_H_
+
+#include "webrtc/base/scoped_ptr.h"
+#include "webrtc/modules/audio_processing/transient/wpd_node.h"
+
+namespace webrtc {
+
+// Tree of a Wavelet Packet Decomposition (WPD).
+//
+// The root node contains all the data provided; for each node in the tree, the
+// left child contains the approximation coefficients extracted from the node,
+// and the right child contains the detail coefficients.
+// It preserves its state, so it can be multiple-called.
+//
+// The number of nodes in the tree will be 2 ^ levels - 1.
+//
+// Implementation details: Since the tree always will be a complete binary tree,
+// it is implemented using a single linear array instead of managing the
+// relationships in each node. For convience is better to use a array that
+// starts in 1 (instead of 0). Taking that into account, the following formulas
+// apply:
+// Root node index: 1.
+// Node(Level, Index in that level): 2 ^ Level + (Index in that level).
+// Left Child: Current node index * 2.
+// Right Child: Current node index * 2 + 1.
+// Parent: Current Node Index / 2 (Integer division).
+class WPDTree {
+ public:
+  // Creates a WPD tree using the data length and coefficients provided.
+  WPDTree(size_t data_length,
+          const float* high_pass_coefficients,
+          const float* low_pass_coefficients,
+          size_t coefficients_length,
+          int levels);
+  ~WPDTree();
+
+  // Returns the number of nodes at any given level.
+  static int NumberOfNodesAtLevel(int level) {
+    return 1 << level;
+  }
+
+  // Returns a pointer to the node at the given level and index(of that level).
+  // Level goes from 0 to levels().
+  // Index goes from 0 to the number of NumberOfNodesAtLevel(level) - 1.
+  //
+  // You can use the following formulas to get any node within the tree:
+  // Notation: (Level, Index of node in that level).
+  // Root node: (0/0).
+  // Left Child: (Current node level + 1, Current node index * 2).
+  // Right Child: (Current node level + 1, Current node index * 2 + 1).
+  // Parent: (Current node level - 1, Current node index / 2) (Integer division)
+  //
+  // If level or index are out of bounds the function will return NULL.
+  WPDNode* NodeAt(int level, int index);
+
+  // Updates all the nodes of the tree with the new data. |data_length| must be
+  // teh same that was used for the creation of the tree.
+  // Returns 0 if correct, and -1 otherwise.
+  int Update(const float* data, size_t data_length);
+
+  // Returns the total number of levels below the root. Root is cosidered level
+  // 0.
+  int levels() const { return levels_; }
+
+  // Returns the total number of nodes.
+  int num_nodes() const { return num_nodes_; }
+
+  // Returns the total number of leaves.
+  int num_leaves() const { return 1 << levels_; }
+
+ private:
+  size_t data_length_;
+  int levels_;
+  int num_nodes_;
+  rtc::scoped_ptr<rtc::scoped_ptr<WPDNode>[]> nodes_;
+};
+
+}  // namespace webrtc
+
+#endif  // WEBRTC_MODULES_AUDIO_PROCESSING_TRANSIENT_WPD_TREE_H_