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/test/unittest.proto

@@ -0,0 +1,50 @@
+syntax = "proto2";
+option optimize_for = LITE_RUNTIME;
+package webrtc.audioproc;
+
+message Test {
+  optional int32 num_reverse_channels = 1;
+  optional int32 num_input_channels = 2;
+  optional int32 num_output_channels = 3;
+  optional int32 sample_rate = 4;
+
+  message Frame {
+  }
+
+  repeated Frame frame = 5;
+
+  optional int32 analog_level_average = 6;
+  optional int32 max_output_average = 7;
+
+  optional int32 has_echo_count = 8;
+  optional int32 has_voice_count = 9;
+  optional int32 is_saturated_count = 10;
+
+  message Statistic {
+    optional int32 instant = 1;
+    optional int32 average = 2;
+    optional int32 maximum = 3;
+    optional int32 minimum = 4;
+  }
+
+  message EchoMetrics {
+    optional Statistic residual_echo_return_loss = 1;
+    optional Statistic echo_return_loss = 2;
+    optional Statistic echo_return_loss_enhancement = 3;
+    optional Statistic a_nlp = 4;
+  }
+
+  optional EchoMetrics echo_metrics = 11;
+
+  message DelayMetrics {
+    optional int32 median = 1;
+    optional int32 std = 2;
+  }
+
+  optional DelayMetrics delay_metrics = 12;
+}
+
+message OutputData {
+  repeated Test test = 1;
+}
+