Disable renderToAssociatedSink by default.

content/renderer/media/user_media_client_impl_unittest.cc

 // Copyright (c) 2012 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 "content/renderer/media/user_media_client_impl.h"
 
 #include <stddef.h>
 
 #include <memory>
 #include <utility>
@@ skipping 605 matching lines @@
   EXPECT_EQ(blink::WebSourceInfo::VideoFacingModeEnvironment, source->facing());
 }
 
 TEST_F(UserMediaClientImplTest, RenderToAssociatedSinkConstraint) {
   // For a null UserMediaRequest (no audio requested), we expect false.
   used_media_impl_->RequestUserMedia();
   EXPECT_FALSE(used_media_impl_->UserMediaRequestHasAutomaticDeviceSelection(
       ms_dispatcher_->audio_input_request_id()));
   used_media_impl_->DeleteRequest(ms_dispatcher_->audio_input_request_id());
 
   // If audio is requested, but no constraint, it should be true.

[hta - Chromium, 2016/05/08 11:45:33]

can you add a comment here as to why it's currently expecting FALSE, with a
crbug.com/<number> link?

   MockConstraintFactory factory;
   blink::WebMediaConstraints audio_constraints =
       factory.CreateWebMediaConstraints();
-  EXPECT_TRUE(AudioRequestHasAutomaticDeviceSelection(
+  EXPECT_FALSE(AudioRequestHasAutomaticDeviceSelection(
       factory.CreateWebMediaConstraints()));
 
   // If the constraint is present, it should dictate the result.
   factory.Reset();
   factory.AddAdvanced().renderToAssociatedSink.setExact(true);
   EXPECT_TRUE(AudioRequestHasAutomaticDeviceSelection(
       factory.CreateWebMediaConstraints()));
 
   factory.Reset();
   factory.AddAdvanced().renderToAssociatedSink.setExact(false);
@@ skipping 37 matching lines @@
   // Now we close the web frame, if in the above Stop() call,
   // UserMediaClientImpl accidentally removed audio track, then video track will
   // be removed again here, which is incorrect.
   used_media_impl_->FrameWillClose();
   blink::WebHeap::collectAllGarbageForTesting();
   EXPECT_EQ(1, ms_dispatcher_->stop_video_device_counter());
   EXPECT_EQ(1, ms_dispatcher_->stop_audio_device_counter());
 }
 
 }  // namespace content