Revert of Remove SkThread.h, include SkMutex.h or SkAtomics.h as appropriate.

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 305 matching lines @@
         '<(skia_include_path)/core/SkSurface.h',
         '<(skia_include_path)/core/SkTArray.h',
         '<(skia_include_path)/core/SkTDArray.h',
         '<(skia_include_path)/core/SkTDStack.h',
         '<(skia_include_path)/core/SkTDict.h',
         '<(skia_include_path)/core/SkTInternalLList.h',
         '<(skia_include_path)/core/SkTRegistry.h',
         '<(skia_include_path)/core/SkTSearch.h',
         '<(skia_include_path)/core/SkTemplates.h',
         '<(skia_include_path)/core/SkTextBlob.h',
+        '<(skia_include_path)/core/SkThread.h',
         '<(skia_include_path)/core/SkTime.h',
         '<(skia_include_path)/core/SkTLazy.h',
         '<(skia_include_path)/core/SkTypeface.h',
         '<(skia_include_path)/core/SkTypes.h',
         '<(skia_include_path)/core/SkUnPreMultiply.h',
         '<(skia_include_path)/core/SkUtils.h',
         '<(skia_include_path)/core/SkWeakRefCnt.h',
         '<(skia_include_path)/core/SkWriter32.h',
         '<(skia_include_path)/core/SkXfermode.h',
 
@@ skipping 57 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',
     ],
 }