Add passthrough GP for cases where no color or coverage should be emitted by GP

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 73 matching lines @@
       '<(skia_src_path)/gpu/GrCoordTransform.cpp',
       '<(skia_src_path)/gpu/GrDefaultGeoProcFactory.cpp',
       '<(skia_src_path)/gpu/GrDefaultGeoProcFactory.h',
       '<(skia_src_path)/gpu/GrDrawContext.cpp',
       '<(skia_src_path)/gpu/GrDrawTarget.cpp',
       '<(skia_src_path)/gpu/GrDrawTarget.h',
       '<(skia_src_path)/gpu/GrFontScaler.cpp',
       '<(skia_src_path)/gpu/GrFontScaler.h',
       '<(skia_src_path)/gpu/GrFragmentProcessor.cpp',
       '<(skia_src_path)/gpu/GrGeometryBuffer.h',
+      '<(skia_src_path)/gpu/GrGeometryProcessor.cpp',
       '<(skia_src_path)/gpu/GrGeometryProcessor.h',
       '<(skia_src_path)/gpu/GrGlyph.h',
       '<(skia_src_path)/gpu/GrGpu.cpp',
       '<(skia_src_path)/gpu/GrGpu.h',
       '<(skia_src_path)/gpu/GrGpuResourceCacheAccess.h',
       '<(skia_src_path)/gpu/GrGpuResourcePriv.h',
       '<(skia_src_path)/gpu/GrGpuResource.cpp',
       '<(skia_src_path)/gpu/GrGpuFactory.cpp',
       '<(skia_src_path)/gpu/GrGpuFactory.h',
       '<(skia_src_path)/gpu/GrIndexBuffer.h',
@@ skipping 342 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',
     ],
   },
 }