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..8c211e5075d12dd559eb32515833f12c65b69dc8 100644
--- a/content/renderer/media/media_stream_audio_processor_options.h
+++ b/content/renderer/media/media_stream_audio_processor_options.h
@@ -8,12 +8,9 @@
 #include <string>
 
 #include "base/platform_file.h"
+#include "third_party/WebKit/public/platform/WebMediaConstraints.h"
 #include "third_party/libjingle/source/talk/app/webrtc/mediastreaminterface.h"
 
-namespace blink {
-class WebMediaConstraints;
-}
-
 namespace webrtc {
 
 class AudioFrame;
@@ -30,26 +27,53 @@ class RTCMediaConstraints;
 using webrtc::AudioProcessing;
 using webrtc::MediaConstraintsInterface;
 
-// 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
-// be added with mandatory status.
-void ApplyFixedAudioConstraints(RTCMediaConstraints* constraints);
-
-// Checks if any audio constraints are set that requires audio processing to
-// be applied. |effects| is the bitmasks telling whether certain platform
-// hardware audio effects are enabled, like hardware echo cancellation. If some
-// hardware effect is enabled, the corresponding software audio processing will
-// be disabled.
-bool NeedsAudioProcessing(const blink::WebMediaConstraints& constraints,
-                          int effects);
-
-// 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);
+// A helper class to parse audio constraints from a blink::WebMediaConstraints
+// object.
+class MediaAudioConstraints {
+ public:
+  // Constraint keys used by audio processing.
+  static const char kEchoCancellation[];
+  static const char kGoogEchoCancellation[];
+  static const char kGoogExperimentalEchoCancellation[];
+  static const char kGoogAutoGainControl[];
+  static const char kGoogExperimentalAutoGainControl[];
+  static const char kGoogNoiseSuppression[];
+  static const char kGoogExperimentalNoiseSuppression[];
+  static const char kGoogHighpassFilter[];
+  static const char kGoogTypingNoiseDetection[];
+  static 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
+  // be added with optional status.
+  static void ApplyFixedAudioConstraints(RTCMediaConstraints* constraints);
+
+  // |effects| is the bitmasks telling whether certain platform
+  // hardware audio effects are enabled, like hardware echo cancellation. If
+  // some hardware effect is enabled, the corresponding software audio
+  // processing will be disabled.
+  MediaAudioConstraints(const blink::WebMediaConstraints& constraints,
+                        int effects);
+  virtual ~MediaAudioConstraints();
+
+  // Checks if any audio constraints are set that requires audio processing to
+  // be applied.
+  bool NeedsAudioProcessing();
+
+  // Gets the property of the constraint named by |key| in |constraints_|.
+  // Returns the constraint's value if the key is found; Otherwise returns the
+  // default value of the constraint.
+  bool GetProperty(const std::string& key);
+
+  // Returns true if all the mandatory constraints in |constraints_| are valid;
+  // Otherwise return false.
+  bool IsValid();
+
+ private:
+  const blink::WebMediaConstraints constraints_;
+  const int effects_;
+};
 
 // Enables the echo cancellation in |audio_processing|.
 void EnableEchoCancellation(AudioProcessing* audio_processing);
@@ -72,7 +96,7 @@ void EnableExperimentalEchoCancellation(AudioProcessing* audio_processing);
 
 // Starts the echo cancellation dump in |audio_processing|.
 void StartEchoCancellationDump(AudioProcessing* audio_processing,
-                  const base::PlatformFile& aec_dump_file);
+                               const base::PlatformFile& aec_dump_file);
 
 // Stops the echo cancellation dump in |audio_processing|.
 // This method has no impact if echo cancellation dump has not been started on