Adds an API for inserting fake devices to internals

third_party/WebKit/Source/modules/mediastream/testing/InternalsMediaStream.h

Index: third_party/WebKit/Source/modules/mediastream/testing/InternalsMediaStream.h
diff --git a/third_party/WebKit/Source/modules/mediastream/testing/InternalsMediaStream.h b/third_party/WebKit/Source/modules/mediastream/testing/InternalsMediaStream.h
new file mode 100644
index 0000000000000000000000000000000000000000..ea65d26f623d6dfd267871fdec27a121ffccfcbc
--- /dev/null
+++ b/third_party/WebKit/Source/modules/mediastream/testing/InternalsMediaStream.h
@@ -0,0 +1,32 @@
+// Copyright 2017 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.
+
+#ifndef InternalsMediaStream_h
+#define InternalsMediaStream_h
+
+#include "wtf/Allocator.h"
+
+namespace blink {
+
+class Internals;
+class MediaDeviceInfo;
+class MediaStreamTrack;
+class MediaTrackConstraints;
+class ScriptPromise;
+class ScriptState;
+
+class InternalsMediaStream {
+  STATIC_ONLY(InternalsMediaStream);
+
+ public:
+  static ScriptPromise addFakeDevice(ScriptState*,
+                                     Internals&,
+                                     const MediaDeviceInfo*,
+                                     const MediaTrackConstraints& capabilities,
+                                     const MediaStreamTrack* dataSource);
+};
+
+}  // namespace blink
+
+#endif  // InternalsMediaStream_h