INPUT element: Deprecate case-insensitive matching for radio button group names.

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 4d3b4c9f8ace5102fcdb2a83f48221b1fd675f96..15db0d4d0df9e7f458d698f697c56f87441595b9 100644
--- a/third_party/WebKit/Source/core/frame/Deprecation.cpp
+++ b/third_party/WebKit/Source/core/frame/Deprecation.cpp
@@ -276,6 +276,12 @@ String Deprecation::deprecationMessage(UseCounter::Feature feature) {
       return "<source src> with a <picture> parent is invalid and therefore "
              "ignored. Please use <source srcset> instead.";
 
+    case UseCounter::RadioNameMatchingASCIICaseless:
+    case UseCounter::RadioNameMatchingCaseFolding:
+      return willBeRemoved(
+          "Case-insensitive matching for <input type=radio name=...>", M57,
+          "6165799291060224");
+
     case UseCounter::ConsoleTimeline:
       return replacedBy("'console.timeline'", "'console.time'");