Report Pointer Lock webkitMovementX/Y attributes as deprecated.

Source/core/frame/UseCounter.cpp

Index: Source/core/frame/UseCounter.cpp
diff --git a/Source/core/frame/UseCounter.cpp b/Source/core/frame/UseCounter.cpp
index 049a0e092c1e191d785ee16567ad874156d5ba9f..8fb948fb86274a3274f8af0488a1f3c9ced384e9 100644
--- a/Source/core/frame/UseCounter.cpp
+++ b/Source/core/frame/UseCounter.cpp
@@ -917,6 +917,12 @@ String UseCounter::deprecationMessage(Feature feature)
     case CSSSelectorPseudoShadow:
         return "::shadow pseudo-element is deprecated. See https://www.chromestatus.com/features/6750456638341120 for more details.";
 
+    case PrefixedMouseEventMovementX:
+        return replacedBy("webkitMovementX", "movementX");
+
+    case PrefixedMouseEventMovementY:
+        return replacedBy("webkitMovementY", "movementY");
+
     // Features that aren't deprecated don't have a deprecation message.
     default:
         return String();