Add JSON serializer to MediaDeviceInfo.

third_party/WebKit/Source/modules/mediastream/MediaDeviceInfo.h

Index: third_party/WebKit/Source/modules/mediastream/MediaDeviceInfo.h
diff --git a/third_party/WebKit/Source/modules/mediastream/MediaDeviceInfo.h b/third_party/WebKit/Source/modules/mediastream/MediaDeviceInfo.h
index 9c893fb47d5c01ec5d6c85aa21492147cbec40b3..3de7534c81f5232081039bba794139fea3685f2d 100644
--- a/third_party/WebKit/Source/modules/mediastream/MediaDeviceInfo.h
+++ b/third_party/WebKit/Source/modules/mediastream/MediaDeviceInfo.h
@@ -33,6 +33,9 @@
 
 namespace blink {
 
+class ScriptState;
+class ScriptValue;
+
 class MODULES_EXPORT MediaDeviceInfo final : public GarbageCollectedFinalized<MediaDeviceInfo>, public ScriptWrappable {
     DEFINE_WRAPPERTYPEINFO();
 public:
@@ -43,6 +46,8 @@ public:
     String label() const;
     String groupId() const;
 
+    ScriptValue toJSONForBinding(ScriptState*);
+
     DEFINE_INLINE_TRACE() { }
 
 private: