Drop deprecation message for xhr.withCredentials for sync requests

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

 /*
  * Copyright (C) 2012 Google, Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 354 matching lines @@
         EditingAppleStyleSpanClass = 461,
         EditingAppleTabSpanClass = 462,
         HTMLImportsAsyncAttribute = 463,
         XMLHttpRequestSynchronous = 465,
         CSSSelectorPseudoUnresolved = 466,
         CSSSelectorPseudoShadow = 467,
         CSSSelectorPseudoContent = 468,
         CSSSelectorPseudoHost = 469,
         CSSSelectorPseudoHostContext = 470,
         CSSDeepCombinator = 471,
-        SyncXHRWithCredentials = 472,

[sof, 2016/05/31 20:32:20]

What's the procedure to follow wrt updating tools/metrics/histograms/ when
retiring a counter?

[foolip, 2016/05/31 21:45:53]

They aren't removed by running the script, and all entries I've removed or seen
removed have remained in histograms.xml. It would be nice if the fact that it's
been removed were somehow propagated to https://www.chromestatus.com/ but my one
and only attempt at this didn't go too well:
https://github.com/GoogleChrome/chromium-dashboard/pull/129

[sof, 2016/06/01 05:34:16]

ok, there'll be a major GC when the list becomes too littered with empty ones, i
guess.

[foolip, 2016/06/01 06:56:20]

Yeah. The way I hope it works out is that each counter gets milestones attached
to it for when it was added, deprecated and removed, that would show up in the
graphs.

         // The above items are available in M37 branch.
 
         UseAsm = 473,
         DOMWindowOpen = 475,
         DOMWindowOpenFeatures = 476,
         MediaStreamTrackGetSources = 478,
         AspectRatioFlexItem = 479,
         DetailsElement = 480,
         DialogElement = 481,
         MapElement = 482,
@@ skipping 901 matching lines @@
     friend class UseCounterTest;
     static int m_muteCount;
 
     CountBits m_countBits;
     BitVector m_CSSFeatureBits;
 };
 
 } // namespace blink
 
 #endif // UseCounter_h