Remove the UseCounter entries for beforeload events

BUG=333318
NOTRY=true

Review URL: https://codereview.chromium.org/212883002

git-svn-id: svn://svn.chromium.org/blink/trunk@170122 bbb929c8-8fbe-4397-9dbb-9b2b20218538

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

@@ -189,11 +189,9 @@ public:
         HTMLAppletElementLegacyCall = 151,
         HTMLEmbedElementLegacyCall = 152,
         HTMLObjectElementLegacyCall = 153,
-        BeforeLoadEvent = 154,
         GetMatchedCSSRules = 155,
         SVGFontInCSS = 156,
         AttributeSpecified = 162, // Removed in DOM4.
-        BeforeLoadEventInIsolatedWorld = 163,
         PrefixedAudioDecodedByteCount = 164,
         PrefixedVideoDecodedByteCount = 165,
         PrefixedVideoDecodedFrameCount = 172,