Add usage counter for each value of webkit-user-modify

third_party/WebKit/Source/core/css/parser/CSSPropertyParser.cpp

Index: third_party/WebKit/Source/core/css/parser/CSSPropertyParser.cpp
diff --git a/third_party/WebKit/Source/core/css/parser/CSSPropertyParser.cpp b/third_party/WebKit/Source/core/css/parser/CSSPropertyParser.cpp
index deae8c986455922f3e6d14b1ec9eaebfe43af1fe..990fd704becf4550067dba8cdddce718b4d7285d 100644
--- a/third_party/WebKit/Source/core/css/parser/CSSPropertyParser.cpp
+++ b/third_party/WebKit/Source/core/css/parser/CSSPropertyParser.cpp
@@ -2019,6 +2019,24 @@ static void countKeywordOnlyPropertyUsage(CSSPropertyID property,
       break;
     }
 
+    case CSSPropertyWebkitUserModify: {
+      switch (valueID) {
+        case CSSValueReadOnly:
+          context->useCounter()->count(UseCounter::CSSValueUserModifyReadOnly);
+          break;
+        case CSSValueReadWrite:
+          context->useCounter()->count(UseCounter::CSSValueUserModifyReadWrite);
+          break;
+        case CSSValueReadWritePlaintextOnly:
+          context->useCounter()->count(
+              UseCounter::CSSValueUserModifyReadWritePlaintextOnly);
+          break;
+        default:
+          NOTREACHED();

[tkent, 2017/02/02 08:01:42]

Remove NOTREACHED().  There are other valid values such as 'inherit' 'initial'.

[Xiaocheng, 2017/02/02 08:10:15]

The current implementation only accepts 'read-write', 'read-only' and
'read-write-plaintext-only' as valid values. Other values will be rejected by
|CSSParserFastPaths::isValidKeywordPropertyAndValue|.

So I think it's correct to put NOTREACHED() here.

[tkent, 2017/02/02 08:21:01]

Ack.  Please go ahead.

+      }
+      break;
+    }
+
     default:
       break;
   }