Cleanup the XML directory in public includes.

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:*',
+        'xml.gyp:xml',
       ],
       'include_dirs': [
         '../include/effects',
         '../include/images',
         '../include/ports',
         '../include/utils',
         '../include/utils/win',
-        '../include/xml',
         '../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',
@@ skipping 161 matching lines @@
         }],
       ],
       'direct_dependent_settings': {
         'include_dirs': [
           '../include/ports',
         ],
       },
     },
   ],
 }