Move JSONValues.cpp/.h to Source/platform/

Source/platform/blink_platform.gypi

 {
   'variables': {
     'platform_files': [
       'exported/Platform.cpp',
       'exported/WebData.cpp',
       'Clock.cpp',
       'Clock.h',
       'DateComponents.cpp',
       'DateComponents.h',
       'Decimal.cpp',
       'Decimal.h',
+      'JSONValues.cpp',
+      'JSONValues.h',
       'Language.cpp',
       'Language.h',
       'LinkHash.cpp',
       'LinkHash.h',
       'Logging.cpp',
       'Logging.h',
       'NotImplemented.cpp',
       'NotImplemented.h',
       'PurgeableBuffer.cpp',
       'PurgeableBuffer.h',
       'SharedBuffer.cpp',
       'SharedBuffer.h',
     ],
     'platform_test_files': [
       'ClockTest.cpp',
       'DecimalTest.cpp',
       'SharedBufferTest.cpp',
     ],
   },
 }