Added a kEchoCancellation constraint to turn off the audio processing.

content/renderer/media/mock_media_constraint_factory.h

Index: content/renderer/media/mock_media_constraint_factory.h
diff --git a/content/renderer/media/mock_media_constraint_factory.h b/content/renderer/media/mock_media_constraint_factory.h
index 6eb261a42f71afde5123ac39272761f88607cfe5..e98cb30429b976e192dd0e902c42d29f09bbcef4 100644
--- a/content/renderer/media/mock_media_constraint_factory.h
+++ b/content/renderer/media/mock_media_constraint_factory.h
@@ -20,8 +20,12 @@ class MockMediaConstraintFactory {
   blink::WebMediaConstraints CreateWebMediaConstraints();
   void AddMandatory(const std::string& key, int value);
   void AddMandatory(const std::string& key, double value);
+  void AddMandatory(const std::string& key, const std::string& value);
+  void AddMandatory(const std::string& key, bool value);
   void AddOptional(const std::string& key, int value);
   void AddOptional(const std::string& key, double value);
+  void AddOptional(const std::string& key, const std::string& value);
+  void AddOptional(const std::string& key, bool value);
   void DisableDefaultAudioConstraints();
 
  private: