[MIGRATED] Make deprecation warnings on XHR's setRequestHeader more accurate

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 2c8a68fd0d79a79c00af42b6df260495b55e3ab1..e0a464d5fafd9aac6704a0000a1c932610dd8089 100644
--- a/Source/core/frame/UseCounter.cpp
+++ b/Source/core/frame/UseCounter.cpp
@@ -955,7 +955,10 @@ String UseCounter::deprecationMessage(Feature feature)
         return "Request.context is deprecated and will be removed in M46 (see: https://www.chromestatus.com/feature/5534702526005248).";
 
     case HeaderValueNotMatchingRFC7230:
-        return "Header values not matching to RFC 7230, will be deprecated (see: https://www.chromestatus.com/feature/6457425448140800).";
+        return "Found a header value that doesn't match the field-content token production (containing invalid octets. see RFC 7230). We are experimenting whether we can throw for such header values (see: https://www.chromestatus.com/feature/6457425448140800).";
+
+    case XHRSetRequestHeaderAffectedByNormalization:
+        return "According to the Fetch Standard, setRequestHeader() must strip leading/trailing whitespaces, but it doesn't currently. We are experimenting whether we can make it conform to the spec (see: https://www.chromestatus.com/feature/6457425448140800). This script will be affected by the change.";
 
     // Features that aren't deprecated don't have a deprecation message.
     default: