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

third_party/WebKit/Source/core/frame/UseCounter.h

Index: third_party/WebKit/Source/core/frame/UseCounter.h
diff --git a/third_party/WebKit/Source/core/frame/UseCounter.h b/third_party/WebKit/Source/core/frame/UseCounter.h
index ff7c319eb6968a3f65f68583a9d3047a57c8f04a..cf718c56c2ea4f28729415462bb63c0d9dec7e10 100644
--- a/third_party/WebKit/Source/core/frame/UseCounter.h
+++ b/third_party/WebKit/Source/core/frame/UseCounter.h
@@ -1448,6 +1448,9 @@ class CORE_EXPORT UseCounter {
     WebNFCWatch = 1795,
     WebNFCCancelWatch = 1796,
     AudioParamCancelAndHoldAtTime = 1797,
+    CSSValueUserModifyReadOnly = 1798,

[Manuel Rego, 2017/02/03 14:12:07]

Not really important but we usually have comments like:
  // The above items are available in M56 branch.

As M57 branch has just happened, maybe it'd be nice to add this.

This makes easier to follow in which releases the use counters
have been introduced.

[Xiaocheng, 2017/02/03 14:35:13]

Thanks, with a question.

Counters starting from 1788 are added in M58, and some of them are merged to M57
(1788-1792 are merged, 1797 is merge-approved).

In this case, where should the comment be put at?

[Manuel Rego, 2017/02/03 14:46:22]

That's a good question and I don't have a good answer for it.

What I think is that it's valuable to have those comments,
maybe we should put it before 1793; and move 1797 just after 1792.
But it can be confusing too.

Dunno if @haraken has the right answer.

+    CSSValueUserModifyReadWrite = 1799,
+    CSSValueUserModifyReadWritePlaintextOnly = 1800,
 
     // Add new features immediately above this line. Don't change assigned
     // numbers of any item, and don't reuse removed slots.