Added a kEchoCancellation constraint to turn off the audio processing.

content/renderer/media/media_stream_video_source_unittest.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <string>
 #include <vector>
 
 #include "base/bind.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/utf_string_conversions.h"
@@ skipping 78 matching lines @@
 
   // Test that the source crops to the requested max width and
   // height even though the camera delivers a larger frame.
   void TestSourceCropFrame(int capture_width,
                            int capture_height,
                            const blink::WebMediaConstraints& constraints,
                            int expected_width,
                            int expected_height) {
     // Expect the source to start capture with the supported resolution.
     blink::WebMediaStreamTrack track =
-        CreateTrackAndStartSource(constraints, capture_width, capture_height ,
+        CreateTrackAndStartSource(constraints, capture_width, capture_height,
                                   30);
 
     MockMediaStreamVideoSink sink;
     MediaStreamVideoSink::AddToVideoTrack(&sink, track);
     EXPECT_EQ(0, sink.number_of_frames());
 
     scoped_refptr<media::VideoFrame> frame =
         media::VideoFrame::CreateBlackFrame(gfx::Size(capture_width,
                                                       capture_height));
     mock_source()->DeliverVideoFrame(frame);
@@ skipping 356 matching lines @@
   EXPECT_TRUE(MediaStreamVideoSource::IsConstraintSupported(
         MediaStreamVideoSource::kMaxAspectRatio));
   EXPECT_TRUE(MediaStreamVideoSource::IsConstraintSupported(
       MediaStreamVideoSource::kMinAspectRatio));
 
   EXPECT_FALSE(MediaStreamVideoSource::IsConstraintSupported(
       "something unsupported"));
 }
 
 }  // namespace content