WTF::ThreadSpecific should use base::ThreadLocalStorage.

third_party/WebKit/Source/wtf/wtf.gypi

 # For GN compatibility, this file can not have any conditions.
 {
     'variables': {
         'wtf_files': [
             'ASCIICType.cpp',
             'ASCIICType.h',
             'AddressSanitizer.h',
             'AddressSpaceRandomization.cpp',
             'AddressSpaceRandomization.h',
             'Alignment.h',
@@ skipping 91 matching lines @@
             'SpinLock.cpp',
             'SpinLock.h',
             'StaticConstructors.h',
             'StdLibExtras.h',
             'StringExtras.h',
             'StringHasher.h',
             'TemporaryChange.h',
             'ThreadRestrictionVerifier.h',
             'ThreadSafeRefCounted.h',
             'ThreadSpecific.h',
-            'ThreadSpecificWin.cpp',
             'Threading.h',
             'ThreadingPrimitives.h',
             'ThreadingPthreads.cpp',
             'ThreadingWin.cpp',
             'TreeNode.h',
             'TypeTraits.h',
             'TypedArrayBase.h',
             'Uint16Array.h',
             'Uint32Array.h',
             'Uint8Array.h',
@@ skipping 101 matching lines @@
             'text/StringBufferTest.cpp',
             'text/StringBuilderTest.cpp',
             'text/StringImplTest.cpp',
             'text/StringOperatorsTest.cpp',
             'text/TextCodecReplacementTest.cpp',
             'text/TextCodecUTF8Test.cpp',
             'text/WTFStringTest.cpp',
         ],
     },
 }