Revert of Remove MediaStreamTrack.getSources().

third_party/WebKit/Source/core/frame/Deprecation.cpp

Index: third_party/WebKit/Source/core/frame/Deprecation.cpp
diff --git a/third_party/WebKit/Source/core/frame/Deprecation.cpp b/third_party/WebKit/Source/core/frame/Deprecation.cpp
index acf4384865e9046d051cf76d82f0d7a297a584c9..abfa91b3c9d142ee79fa8f1c6f0463dbd6092ef6 100644
--- a/third_party/WebKit/Source/core/frame/Deprecation.cpp
+++ b/third_party/WebKit/Source/core/frame/Deprecation.cpp
@@ -391,6 +391,10 @@
       return replacedBy("'Performance.onwebkitresourcetimingbufferfull'",
                         "'Performance.onresourcetimingbufferfull'");
 
+    case UseCounter::MediaStreamTrackGetSources:
+      return willBeRemoved("MediaStreamTrack.getSources", M56,
+                           "4765305641369600");
+
     case UseCounter::WebAnimationHyphenatedProperty:
       return "Hyphenated property names in Web Animations keyframes are "
              "invalid and therefore ignored. Please use camelCase instead.";