Added a kEchoCancellation constraint to turn off the audio processing.

content/renderer/media/media_stream_audio_processor_options.h

Index: content/renderer/media/media_stream_audio_processor_options.h
diff --git a/content/renderer/media/media_stream_audio_processor_options.h b/content/renderer/media/media_stream_audio_processor_options.h
index 3ad41100b4c78f1157519b2598df4435fd692f1b..9ee48224fff6fbf25e5c49316f109732d266fded 100644
--- a/content/renderer/media/media_stream_audio_processor_options.h
+++ b/content/renderer/media/media_stream_audio_processor_options.h
@@ -8,6 +8,7 @@
 #include <string>
 
 #include "base/platform_file.h"
+#include "content/public/common/media_stream_request.h"

[perkj_chrome, 2014/04/08 10:28:12]

this seems like a weird inclusion. This is not for a new request right and
should probably not be dependent on classes used for requesting media devices
from the browser process.

Is MediaStreamType the correct type selector?

[no longer working on chromium, 2014/04/11 08:56:30]

Done.

 #include "third_party/libjingle/source/talk/app/webrtc/mediastreaminterface.h"
 
 namespace blink {
@@ -30,6 +31,19 @@ class RTCMediaConstraints;
 using webrtc::AudioProcessing;
 using webrtc::MediaConstraintsInterface;
 
+// Constraint keys used by audio processing.
+// Specified by draft-alvestrand-constraints-resolution-00b.

[perkj_chrome, 2014/04/08 10:28:12]

No- this comment is wrong. this draft has nothing to do with these constraints. 
Document them please. 

[no longer working on chromium, 2014/04/11 08:56:30]

removed.

+extern const char kEchoCancellation[];
+extern const char kGoogEchoCancellation[];
+extern const char kGoogExperimentalEchoCancellation[];
+extern const char kGoogAutoGainControl[];
+extern const char kGoogExperimentalAutoGainControl[];
+extern const char kGoogNoiseSuppression[];
+extern const char kGoogExperimentalNoiseSuppression[];
+extern const char kGoogHighpassFilter[];
+extern const char kGoogTypingNoiseDetection[];
+extern const char kGoogAudioMirroring[];
+
 // Merge |constraints| with |kDefaultAudioConstraints|. For any key which exists
 // in both, the value from |constraints| is maintained, including its
 // mandatory/optional status. New values from |kDefaultAudioConstraints| will
@@ -42,14 +56,16 @@ void ApplyFixedAudioConstraints(RTCMediaConstraints* constraints);
 // hardware effect is enabled, the corresponding software audio processing will
 // be disabled.
 bool NeedsAudioProcessing(const blink::WebMediaConstraints& constraints,
-                          int effects);
+                          int effects, MediaStreamType type);
 
 // Gets the property named by |key| from the |constraints|.
 // Returns true if the key is found and has a valid boolean value; Otherwise
 // false.
 bool GetPropertyFromConstraints(
-    const MediaConstraintsInterface* constraints,
-    const std::string& key);
+    const blink::WebMediaConstraints& constraints,
+    const std::string& key,
+    int effects,
+    MediaStreamType type);
 
 // Enables the echo cancellation in |audio_processing|.
 void EnableEchoCancellation(AudioProcessing* audio_processing);