Update common_audio

Corresponds to upstream commit 524e9b043e7e86fd72353b987c9d5f6a1ebf83e1

Update notes:

 * Moved src/ to webrtc/ to easily diff against the third_party/webrtc
   in the chromium tree

 * ARM/NEON/MIPS support is not yet hooked up

 * Tests have not been copied

webrtc/modules/audio_processing/debug.proto

@@ -0,0 +1,37 @@
+syntax = "proto2";
+option optimize_for = LITE_RUNTIME;
+package webrtc.audioproc;
+
+message Init {
+  optional int32 sample_rate = 1;
+  optional int32 device_sample_rate = 2;
+  optional int32 num_input_channels = 3;
+  optional int32 num_output_channels = 4;
+  optional int32 num_reverse_channels = 5;
+}
+
+message ReverseStream {
+  optional bytes data = 1;
+}
+
+message Stream {
+  optional bytes input_data = 1;
+  optional bytes output_data = 2;
+  optional int32 delay = 3;
+  optional sint32 drift = 4;
+  optional int32 level = 5;
+}
+
+message Event {
+  enum Type {
+    INIT = 0;
+    REVERSE_STREAM = 1;
+    STREAM = 2;
+  }
+
+  required Type type = 1;
+
+  optional Init init = 2;
+  optional ReverseStream reverse_stream = 3;
+  optional Stream stream = 4;
+}