Add GrSet class built on top of RedBlackTree

gyp/gpu.gypi

 # 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
 #
 {
   'variables': {
     'skgpu_sources': [
@@ skipping 85 matching lines @@
       '<(skia_src_path)/gpu/GrRectanizer.cpp',
       '<(skia_src_path)/gpu/GrRectanizer.h',
       '<(skia_src_path)/gpu/GrRectanizer_skyline.cpp',
       '<(skia_src_path)/gpu/GrRedBlackTree.h',
       '<(skia_src_path)/gpu/GrRenderTarget.cpp',
       '<(skia_src_path)/gpu/GrReducedClip.cpp',
       '<(skia_src_path)/gpu/GrReducedClip.h',
       '<(skia_src_path)/gpu/GrResource.cpp',
       '<(skia_src_path)/gpu/GrResourceCache.cpp',
       '<(skia_src_path)/gpu/GrResourceCache.h',
+      '<(skia_src_path)/gpu/GrSet.h',
       '<(skia_src_path)/gpu/GrStencil.cpp',
       '<(skia_src_path)/gpu/GrStencil.h',
       '<(skia_src_path)/gpu/GrStencilAndCoverPathRenderer.cpp',
       '<(skia_src_path)/gpu/GrStencilAndCoverPathRenderer.h',
       '<(skia_src_path)/gpu/GrStencilBuffer.cpp',
       '<(skia_src_path)/gpu/GrStencilBuffer.h',
       '<(skia_src_path)/gpu/GrTBSearch.h',
       '<(skia_src_path)/gpu/GrSWMaskHelper.cpp',
       '<(skia_src_path)/gpu/GrSWMaskHelper.h',
       '<(skia_src_path)/gpu/GrSoftwarePathRenderer.cpp',
@@ skipping 162 matching lines @@
     ],
     'skgpu_null_gl_sources': [
       '<(skia_src_path)/gpu/gl/GrGLCreateNullInterface.cpp',
 
       # Sk files
       '<(skia_include_path)/gpu/gl/SkNullGLContext.h',
       '<(skia_src_path)/gpu/gl/SkNullGLContext.cpp',
     ],
   },
 }