Deprecate case-insensitive matching for |usemap| attribute

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 366d162cd0394bb64a617eb822317265f2a27f42..488f21ab633633dc3c15848f8199f6295103b1d0 100644
--- a/third_party/WebKit/Source/core/frame/Deprecation.cpp
+++ b/third_party/WebKit/Source/core/frame/Deprecation.cpp
@@ -208,6 +208,11 @@ String Deprecation::deprecationMessage(UseCounter::Feature feature) {
              "deprecated. Please pass the index argument as well: "
              "insertRule(x, 0).";
 
+    case UseCounter::MapNameMatchingASCIICaseless:
+    case UseCounter::MapNameMatchingUnicodeLower:
+      return willBeRemoved("Case-insensitive matching for usemap attribute",
+                           M58, "5760965337415680");
+
     case UseCounter::PrefixedVideoSupportsFullscreen:
       return replacedBy("'HTMLVideoElement.webkitSupportsFullscreen'",
                         "'Document.fullscreenEnabled'");