Move sync code to include/, switch from using platform define to a proxy header in core/

gyp/ports.gyp

 # Port-specific Skia library code.
 {
   'targets': [
     {
       'target_name': 'ports',
       'product_name': 'skia_ports',
       'type': 'static_library',
       'standalone_static_library': 1,
       'dependencies': [
         'core.gyp:*',
       ],
       'include_dirs': [
         '../include/effects',
         '../include/images',
         '../include/ports',
         '../include/utils',
         '../include/utils/win',
         '../src/core',
         '../src/lazy',
         '../src/ports',
         '../src/sfnt',
         '../src/utils',
       ],
       'sources': [
-        '../src/ports/SkAtomics_sync.h',
-        '../src/ports/SkAtomics_win.h',
-        '../src/ports/SkMutex_pthread.h',
-        '../src/ports/SkMutex_win.h',
         '../src/ports/SkDebug_nacl.cpp',
         '../src/ports/SkDebug_stdio.cpp',
         '../src/ports/SkDebug_win.cpp',
 
         '../src/fonts/SkFontMgr_indirect.cpp',
         '../src/fonts/SkRemotableFontMgr.cpp',
         '../src/ports/SkFontHost_win.cpp',
         '../src/ports/SkFontMgr_default_gdi.cpp',
         '../src/ports/SkFontMgr_default_dw.cpp',
         '../src/ports/SkFontMgr_win_dw.cpp',
         '../src/ports/SkRemotableFontMgr_win_dw.cpp',
         '../src/ports/SkScalerContext_win_dw.cpp',
         '../src/ports/SkScalerContext_win_dw.h',
         '../src/ports/SkTypeface_win_dw.cpp',
         '../src/ports/SkTypeface_win_dw.h',
 
         '../src/ports/SkGlobalInitialization_default.cpp',
         '../src/ports/SkMemory_malloc.cpp',
-        '../src/ports/SkMutex_pthread.h',
-        '../src/ports/SkMutex_win.h',
         '../src/ports/SkOSFile_posix.cpp',
         '../src/ports/SkOSFile_stdio.cpp',
         '../src/ports/SkOSFile_win.cpp',
         '../src/ports/SkDiscardableMemory_none.cpp',
         '../src/ports/SkTime_Unix.cpp',
         '../src/ports/SkTime_win.cpp',
         '../src/ports/SkTLS_pthread.cpp',
         '../src/ports/SkTLS_win.cpp',
 
         '../include/ports/SkFontConfigInterface.h',
@@ skipping 129 matching lines @@
         }],
       ],
       'direct_dependent_settings': {
         'include_dirs': [
           '../include/ports',
         ],
       },
     },
   ],
 }