The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/7aee942e5dd7a866708984cf5aab977a5e35af72

commit 7aee942e5dd7a866708984cf5aab977a5e35af72
Author: tkent <tkent@chromium.org>
Date: Thu Apr 06 11:29:13 2017

Count 'icon' attribute of MENUITEM element.

Because MENUITEM element isn't enabled in production, this CL adds counting code
in HTMLUnknownElement too.

BUG= 681444 

Review-Url: https://codereview.chromium.org/2805633002
Cr-Commit-Position: refs/heads/master@{#462425}

[modify] https://crrev.com/7aee942e5dd7a866708984cf5aab977a5e35af72/third_party/WebKit/Source/core/frame/UseCounter.h
[modify] https://crrev.com/7aee942e5dd7a866708984cf5aab977a5e35af72/third_party/WebKit/Source/core/html/HTMLMenuItemElement.cpp
[modify] https://crrev.com/7aee942e5dd7a866708984cf5aab977a5e35af72/third_party/WebKit/Source/core/html/HTMLMenuItemElement.h
[modify] https://crrev.com/7aee942e5dd7a866708984cf5aab977a5e35af72/third_party/WebKit/Source/core/html/HTMLUnknownElement.cpp
[modify] https://crrev.com/7aee942e5dd7a866708984cf5aab977a5e35af72/third_party/WebKit/Source/core/html/HTMLUnknownElement.h
[modify] https://crrev.com/7aee942e5dd7a866708984cf5aab977a5e35af72/tools/metrics/histograms/histograms.xml