Add the 'lighter' composite operation to feComposite.

Source/platform/graphics/filters/FEComposite.cpp

 /*
  * Copyright (C) 2004, 2005, 2006, 2007 Nikolas Zimmermann <zimmermann@kde.org>
  * Copyright (C) 2004, 2005 Rob Buis <buis@kde.org>
  * Copyright (C) 2005 Eric Seidel <eric@webkit.org>
  * Copyright (C) 2009 Dirk Schulze <krit@webkit.org>
  * Copyright (C) Research In Motion Limited 2010. All rights reserved.
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
@@ skipping 166 matching lines @@
     case FECOMPOSITE_OPERATOR_OVER:
         return SkXfermode::kSrcOver_Mode;
     case FECOMPOSITE_OPERATOR_IN:
         return SkXfermode::kSrcIn_Mode;
     case FECOMPOSITE_OPERATOR_OUT:
         return SkXfermode::kSrcOut_Mode;
     case FECOMPOSITE_OPERATOR_ATOP:
         return SkXfermode::kSrcATop_Mode;
     case FECOMPOSITE_OPERATOR_XOR:
         return SkXfermode::kXor_Mode;
+    case FECOMPOSITE_OPERATOR_LIGHTER:
+        return SkXfermode::kPlus_Mode;
     default:
         ASSERT_NOT_REACHED();
         return SkXfermode::kSrcOver_Mode;
     }
 }
 
 PassRefPtr<SkImageFilter> FEComposite::createImageFilter(SkiaImageFilterBuilder* builder)
 {
     return createImageFilterInternal(builder, true);
 }
@@ skipping 33 matching lines @@
         break;
     case FECOMPOSITE_OPERATOR_ATOP:
         ts << "ATOP";
         break;
     case FECOMPOSITE_OPERATOR_XOR:
         ts << "XOR";
         break;
     case FECOMPOSITE_OPERATOR_ARITHMETIC:
         ts << "ARITHMETIC";
         break;
+    case FECOMPOSITE_OPERATOR_LIGHTER:
+        ts << "LIGHTER";
+        break;
     }
     return ts;
 }
 
 TextStream& FEComposite::externalRepresentation(TextStream& ts, int indent) const
 {
     writeIndent(ts, indent);
     ts << "[feComposite";
     FilterEffect::externalRepresentation(ts);
     ts << " operation=\"" << m_type << "\"";
     if (m_type == FECOMPOSITE_OPERATOR_ARITHMETIC)
         ts << " k1=\"" << m_k1 << "\" k2=\"" << m_k2 << "\" k3=\"" << m_k3 << "\" k4=\"" << m_k4 << "\"";
     ts << "]\n";
     inputEffect(0)->externalRepresentation(ts, indent + 1);
     inputEffect(1)->externalRepresentation(ts, indent + 1);
     return ts;
 }
 
 } // namespace blink