Fix Gamma enum in DstColorSpace metric

third_party/WebKit/Source/platform/graphics/BitmapImageMetrics.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef BitmapImageMetrics_h
 #define BitmapImageMetrics_h
 
 #include "platform/PlatformExport.h"
 #include "platform/graphics/ImageOrientation.h"
 #include "third_party/skia/include/core/SkColorSpace.h"
@@ skipping 16 matching lines @@
         ImageBMP = 6,
         DecodedImageTypeEnumEnd = ImageBMP + 1
     };
 
     enum Gamma {
         // Values synced with 'Gamma' in src/tools/metrics/histograms/histograms.xml
         GammaLinear = 0,
         GammaSRGB = 1,
         Gamma2Dot2 = 2,
         GammaNonStandard = 3,
-        GammaEmpty = 4,
-        GammaNull = 5,
-        GammaFail = 6,
+        GammaNull = 4,
+        GammaFail = 5,
         GammaEnd = GammaFail + 1,
     };
 
     static void countDecodedImageType(const String& type);
     static void countImageOrientation(const ImageOrientationEnum);
     static void countGamma(SkColorSpace*);
 };
 
 } // namespace blink
 
 #endif