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

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

Index: third_party/WebKit/Source/core/frame/UseCounter.h
diff --git a/third_party/WebKit/Source/core/frame/UseCounter.h b/third_party/WebKit/Source/core/frame/UseCounter.h
index 18b8b6e0d2efb4cd7e751ef7c99f176de18c3e12..9c6ef824c141e80731ea2ee1667ff523bf45866a 100644
--- a/third_party/WebKit/Source/core/frame/UseCounter.h
+++ b/third_party/WebKit/Source/core/frame/UseCounter.h
@@ -795,7 +795,6 @@ class CORE_EXPORT UseCounter {
     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 keep for historical reference?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,