Enable platform echo cancellation through the AudioRecord path.

content/public/common/media_stream_request.h

Index: content/public/common/media_stream_request.h
diff --git a/content/public/common/media_stream_request.h b/content/public/common/media_stream_request.h
index e6870e150b09d024996e7f5eaa6806bea062b22b..dbb4db2620708daf12a44adc8ee0bcae2f37621e 100644
--- a/content/public/common/media_stream_request.h
+++ b/content/public/common/media_stream_request.h
@@ -80,7 +80,8 @@ struct CONTENT_EXPORT MediaStreamDevice {
       const std::string& name,
       int sample_rate,
       int channel_layout,
-      int frames_per_buffer);
+      int frames_per_buffer,
+      bool use_platform_aec);
 
   ~MediaStreamDevice();
 
@@ -106,14 +107,16 @@ struct CONTENT_EXPORT MediaStreamDevice {
   // in media::AudioParameters.
   struct AudioDeviceParameters {
     AudioDeviceParameters()
-        : sample_rate(), channel_layout(), frames_per_buffer() {
+        : sample_rate(), channel_layout(), frames_per_buffer(),
+          use_platform_aec(false) {
     }
 
     AudioDeviceParameters(int sample_rate, int channel_layout,
-                          int frames_per_buffer)
+                          int frames_per_buffer, bool use_platform_aec)
         : sample_rate(sample_rate),
           channel_layout(channel_layout),
-          frames_per_buffer(frames_per_buffer) {
+          frames_per_buffer(frames_per_buffer),
+          use_platform_aec(use_platform_aec) {
     }
 
     // Preferred sample rate in samples per second for the device.
@@ -129,6 +132,9 @@ struct CONTENT_EXPORT MediaStreamDevice {
     // expected browser side settings and avoid unnecessary buffering.
     // See media::AudioParameters for more.
     int frames_per_buffer;
+
+    // See media::AudioParameters.
+    bool use_platform_aec;
   };
 
   // These below two member variables are valid only when the type of device is