Replace SkFunction with std::function

gyp/core.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 'core' 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 380 matching lines @@
         '<(skia_include_path)/core/SkUnPreMultiply.h',
         '<(skia_include_path)/core/SkUtils.h',
         '<(skia_include_path)/core/SkWriter32.h',
         '<(skia_include_path)/core/SkXfermode.h',
 
         # private
         '<(skia_include_path)/private/SkAtomics.h',
         '<(skia_include_path)/private/SkChecksum.h',
         '<(skia_include_path)/private/SkFloatBits.h',
         '<(skia_include_path)/private/SkFloatingPoint.h',
-        '<(skia_include_path)/private/SkFunction.h',
         '<(skia_include_path)/private/SkGpuFenceSync.h',
         '<(skia_include_path)/private/SkMiniRecorder.h',
         '<(skia_include_path)/private/SkMutex.h',
         '<(skia_include_path)/private/SkOnce.h',
         '<(skia_include_path)/private/SkOncePtr.h',
         '<(skia_include_path)/private/SkRecords.h',
         '<(skia_include_path)/private/SkSemaphore.h',
         '<(skia_include_path)/private/SkSpinlock.h',
         '<(skia_include_path)/private/SkTemplates.h',
         '<(skia_include_path)/private/SkTHash.h',
@@ skipping 59 matching lines @@
         '<(skia_src_path)/pathops/SkPathOpsLine.h',
         '<(skia_src_path)/pathops/SkPathOpsPoint.h',
         '<(skia_src_path)/pathops/SkPathOpsQuad.h',
         '<(skia_src_path)/pathops/SkPathOpsRect.h',
         '<(skia_src_path)/pathops/SkPathOpsTSect.h',
         '<(skia_src_path)/pathops/SkPathOpsTypes.h',
         '<(skia_src_path)/pathops/SkPathWriter.h',
         '<(skia_src_path)/pathops/SkReduceOrder.h',
     ],
 }