Link against chromiumcontent.dll

* vendor/libchromiumcontent 4aae27b...15ada44 (3):
  > Include chromiumcontent.dll's import library
  > Export sandbox/ headers
  > Mention that Python is required to build

brightray/brightray.gyp

@@ -70,6 +70,13 @@
             ],
           },
         }],
+        ['OS=="win"', {
+          'link_settings': {
+            'libraries': [
+              '<(libchromiumcontent_library_dir)/chromiumcontent.dll.lib',
+            ],
+          },
+        }],
       ],
     },
   ],