Remove -internals-media-controls-cast-button as web exposed CSS selector.

third_party/WebKit/Source/core/frame/UseCounter.h

 /*
  * Copyright (C) 2012 Google, Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 777 matching lines @@
     RTCPeerConnectionSetLocalDescriptionLegacyNoSuccessCallback = 1052,
     RTCPeerConnectionSetLocalDescriptionLegacyNoFailureCallback = 1053,
     RTCPeerConnectionSetLocalDescriptionLegacyCompliant = 1054,
     RTCPeerConnectionSetRemoteDescriptionLegacyNoSuccessCallback = 1055,
     RTCPeerConnectionSetRemoteDescriptionLegacyNoFailureCallback = 1056,
     RTCPeerConnectionSetRemoteDescriptionLegacyCompliant = 1057,
     RTCPeerConnectionGetStatsLegacyNonCompliant = 1058,
     NodeFilterIsFunction = 1059,
     NodeFilterIsObject = 1060,
     CSSSelectorInternalPseudoListBox = 1062,
-    CSSSelectorInternalMediaControlsCastButton = 1063,

[jochen (gone - plz use gerrit), 2017/03/10 11:54:33]

nit. keep for historical reference?

[mlamouri (slow - plz ping), 2017/03/13 12:27:07]

My understanding is that we do remove them from UseCounter but keep them in
histograms.xml. Do you think we should do something different?

[jochen (gone - plz use gerrit), 2017/03/13 19:41:53]

what's the point of removing this here?

[mlamouri (slow - plz ping), 2017/03/13 21:04:28]

Avoid dead code I guess. histograms.xml being there for history.

     CSSSelectorInternalMediaControlsOverlayCastButton = 1064,
     CSSSelectorInternalPseudoSpatialNavigationFocus = 1065,
     SameOriginTextScript = 1066,
     SameOriginApplicationScript = 1067,
     SameOriginOtherScript = 1068,
     CrossOriginTextScript = 1069,
     CrossOriginApplicationScript = 1070,
     CrossOriginOtherScript = 1071,
     SVG1DOMSVGTests = 1072,
     DisableRemotePlaybackAttribute = 1074,
@@ skipping 786 matching lines @@
     // Tracks what features/properties need to be reported to the legacy
     // histograms.
     BitVector m_featureBits;
     BitVector m_CSSBits;
   } m_legacyCounter;
 };
 
 }  // namespace blink
 
 #endif  // UseCounter_h