Added GrGLBlend.h|cpp with helper function AppendPorterDuffBlend() in preparation for SkComposeShad…

gyp/gpu.gypi

 # Copyright 2015 Google Inc.
 #
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 # Include this gypi to include all 'gpu' files
 # The parent gyp/gypi file must define
 #       'skia_src_path'     e.g. skia/trunk/src
 #       'skia_include_path' e.g. skia/trunk/include
 #
 # The skia build defines these in common_variables.gypi
@@ skipping 251 matching lines @@
       '<(skia_src_path)/gpu/effects/GrSingleTextureEffect.h',
       '<(skia_src_path)/gpu/effects/GrTextureDomain.cpp',
       '<(skia_src_path)/gpu/effects/GrTextureDomain.h',
       '<(skia_src_path)/gpu/effects/GrTextureStripAtlas.cpp',
       '<(skia_src_path)/gpu/effects/GrTextureStripAtlas.h',
       '<(skia_src_path)/gpu/effects/GrYUVtoRGBEffect.cpp',
       '<(skia_src_path)/gpu/effects/GrYUVtoRGBEffect.h',
 
       '<(skia_src_path)/gpu/gl/GrGLAssembleInterface.cpp',
       '<(skia_src_path)/gpu/gl/GrGLAssembleInterface.h',
+      '<(skia_src_path)/gpu/gl/GrGLBlend.cpp',
+      '<(skia_src_path)/gpu/gl/GrGLBlend.h',
       '<(skia_src_path)/gpu/gl/GrGLBufferImpl.cpp',
       '<(skia_src_path)/gpu/gl/GrGLBufferImpl.h',
       '<(skia_src_path)/gpu/gl/GrGLCaps.cpp',
       '<(skia_src_path)/gpu/gl/GrGLCaps.h',
       '<(skia_src_path)/gpu/gl/GrGLContext.cpp',
       '<(skia_src_path)/gpu/gl/GrGLContext.h',
       '<(skia_src_path)/gpu/gl/GrGLCreateNativeInterface_none.cpp',
       '<(skia_src_path)/gpu/gl/GrGLDefaultInterface_none.cpp',
       '<(skia_src_path)/gpu/gl/GrGLDefines.h',
       '<(skia_src_path)/gpu/gl/GrGLGeometryProcessor.cpp',
@@ skipping 150 matching lines @@
       '<(skia_src_path)/gpu/gl/debug/SkDebugGLContext.cpp',
       '<(skia_src_path)/gpu/gl/debug/SkDebugGLContext.h',
     ],
     'skgpu_null_gl_sources': [
       '<(skia_src_path)/gpu/gl/GrGLCreateNullInterface.cpp',
       '<(skia_src_path)/gpu/gl/SkNullGLContext.cpp',
       '<(skia_include_path)/gpu/gl/SkNullGLContext.h',
     ],
   },
 }