Remove deprecated URL attribute alias from EventSource interface

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 224 matching lines @@
         PrefixedMinDevicePixelRatioMediaFeature = 235,
         PrefixedTransform3dMediaFeature = 237,
         PrefixedStorageQuota = 240,
         ResetReferrerPolicy = 243,
         CaseInsensitiveAttrSelectorMatch = 244, // Case-insensitivity dropped from specification.
         FormNameAccessForImageElement = 246,
         FormNameAccessForPastNamesMap = 247,
         FormAssociationByParser = 248,
         SVGSVGElementInDocument = 250,
         SVGDocumentRootElement = 251,
-        EventSourceURL = 254,
         WorkerSubjectToCSP = 257,
         WorkerAllowedByChildBlockedByScript = 258,
         DeprecatedWebKitGradient = 260,
         DeprecatedWebKitLinearGradient = 261,
         DeprecatedWebKitRepeatingLinearGradient = 262,
         DeprecatedWebKitRadialGradient = 263,
         DeprecatedWebKitRepeatingRadialGradient = 264,
         PrefixedImageSmoothingEnabled = 267,
         UnprefixedImageSmoothingEnabled = 268,
         // The above items are available in M34 branch.
@@ skipping 456 matching lines @@
     bool recordMeasurement(Feature feature) { return m_countBits.recordMeasurement(feature); }
     void updateMeasurements();
 
     CountBits m_countBits;
     BitVector m_CSSFeatureBits;
 };
 
 } // namespace blink
 
 #endif // UseCounter_h