Fix selection of "no audio processing" mode.

content/renderer/media/media_stream_audio_processor_options.cc

Index: content/renderer/media/media_stream_audio_processor_options.cc
diff --git a/content/renderer/media/media_stream_audio_processor_options.cc b/content/renderer/media/media_stream_audio_processor_options.cc
index 9d13b1a6be0087902f99cb47fd60056fc622c4a2..e62831c00873ba7f1f54b2e709599cb4f950d441 100644
--- a/content/renderer/media/media_stream_audio_processor_options.cc
+++ b/content/renderer/media/media_stream_audio_processor_options.cc
@@ -18,6 +18,7 @@
 #include "base/strings/utf_string_conversions.h"
 #include "build/build_config.h"
 #include "content/common/media/media_stream_options.h"
+#include "content/renderer/media/media_stream_constraints_util.h"
 #include "content/renderer/media/media_stream_source.h"
 #include "media/audio/audio_parameters.h"
 #include "third_party/webrtc/modules/audio_processing/include/audio_processing.h"
@@ -171,9 +172,12 @@ MediaAudioConstraints::MediaAudioConstraints(
   // - gUM has a specific kMediaStreamSource, which is used by tab capture
   //   and screen capture.
   // - |kEchoCancellation| is explicitly set to false.
-  std::string value_str;
+  bool echo_constraint;
   if (!constraints.basic().mediaStreamSource.isEmpty() ||
-      !constraints.basic().echoCancellation.matches(true)) {
+      (GetConstraintValueAsBoolean(
+           constraints, &blink::WebMediaTrackConstraintSet::echoCancellation,
+           &echo_constraint) &&
+       echo_constraint == false)) {
     default_audio_processing_constraint_value_ = false;
   }
 }